Is there a right time to turn pro?

NEW YORK -- John Isner, all 6-feet-9 of him, is an overnight sensation four years in the making.

He played tennis in the relative anonymity of the University of Georgia and led the Bulldogs to the 2007 NCAA championship, reaching the singles final. And then -- well, then Isner exploded like his searing 140-mph serve.

In June, after Isner won a Futures event in Chico, Calif., his ATP ranking was No. 839. In July, after winning a Challenger in Lexington, it rose to No. 745. In August, he won five matches at the ATP event in Washington -- beating No. 12-ranked Tommy Haas in the process -- and reached the final. Even though Isner lost to Andy Roddick, his ranking soared to No. 416.

Today, the hard-serving 22-year-old is No. 184 -- and rising with a bullet. He knocked off No. 26 seed Jarkko Nieminen in the first round and, if he beats qualifier Rik De Voest later Wednesday, he's looking at a third-round match with Roger Federer.

Sam Querrey took a more immediate route to professional tennis. He turned down a full scholarship at Southern California and, at the age of 18, turned pro last year. Querrey had a nice flurry the past month -- winning six of eight ATP matches and reaching a Challenger final in Vancouver -- and although he is four years younger than Isner, finds himself ranked No. 48 in the world.

"I'm the biggest go-to-college guy out here," said Paul Goldstein, Stanford Class of 1998 and the only college graduate in the men's top 100. "But, more than anyone I've seen in the last five, six years, Sam's got a legitimate argument to turn pro."

Isner, for his part, said that he wouldn't -- couldn't, really -- have done it any other way.

"I wasn't that good as a junior [player]," Isner said. "Going pro would have been a horrible decision. I'm physically much stronger and more mature because of college. I stayed for four years because I liked it. I didn't want to leave, it was so much fun."

Although college is a mandatory stop for football and, to some extent, basketball players with professional aspirations, ascendant junior tennis players don't often give it the old college try. The most talented players -- particularly on the international side -- jump straight to the pros. The endorsement money, which can drift into seven figures, is too good to resist.

The competition at the college level, historically, has been less intense. That is changing. International players are coming to the United States in increasing numbers and competing with Americans for scholarships. Germany's Benjamin Becker, who helped Baylor win the 2004 NCAA championship, was a three-time All-American and Academic All-Big 12 choice. He's ranked No. 50.

According to Casey Angle, director of information for the Intercollegiate Tennis Association, the average number of non-Americans ranked among the top 100 college players has risen from 20-30 in the early 1990s to 45-60 today.

John McEnroe (Stanford 1977-78) and Jimmy Connors (1971 NCAA singles champion for UCLA) both spent time in college, as did a number of their peers. Arthur Ashe, who won Wimbledon in 1975, is the last college graduate to win a Grand Slam event. Brian Teacher, who won the 1980 Australian Open, left UCLA just shy of a degree in economics to turn pro in 1976; he graduated later and went to USC's business school.

Today's players seem less inclined to go the college route.

Seven of the 10 U.S. women ranked among the top 100 -- including the best two, Serena and Venus Williams -- did not attend college. Those who did: No. 60 Laura Granville (two years at Stanford); No. 77 Lilia Osterloh (one year at Stanford); and No. 75 Jill Craybas (four years between Texas and Florida), the 1996 singles champion and the only woman to be a member of a national championship team with two schools. Craybas is also the only woman ranked among the top 100 with a college degree -- in telecommunications.

Five of the nine American men ranked in the top 100 did not attend college. No. 6 James Blake attended Harvard for two years; No. 67 Michael Russell played at the University of Miami for one year; and No. 71 Amer Delic played three years at Illinois. Goldstein, who earned a degree in human biology, helped lead Stanford to four NCAA team titles and earned four All-America designations.

"I won the Kalamazoo 18s in 1993 and 1994 and got a wild card into the U.S. Open," Goldstein said. "I won 18 games in two three-set matches. Clearly, I wasn't ready for pro tennis."

Room service?
When the phone call came in July, Jesse Levine thought it was one of his buddies pulling a prank. The request to be Federer's guest for 10 days in Dubai, however, turned out to be genuine.

"Me hitting with Roger Federer at a five-star hotel," Levine said. "I know, it's crazy."

Levine, who completed his freshman year at the University of Florida in the spring -- he maintained a perfect 4.0 average -- was one of three workout partners recruited to practice with Federer in the 100-degree heat. He ate lunch with Federer twice and played two competitive sets, losing them both 6-4. He gave the Swiss player two Gators shirts and, this week at the U.S. Open, the world's No. 1 player reciprocated, passing along an exclusive Federer baseball cap.

If an 18-year-old has tennis as his only priority, the tour can chew you up and spit you out before you even get started. I always had other outside interests, and sometimes those distractions were a good thing.

--Paul Goldstein

Hobnobbing with perhaps the greatest player of all time was not the reason, Levine insisted, he elected to leave school and turn professional here.

"It was one of the hardest decisions I've ever had to make," he said after losing his Grand Slam debut, in straight sets to Nikolay Davydenko. "In order to improve, I need to play against players who are better than me.

"You can always go back to school later, but you can't always go back to pro tennis. That's the way I look at it."

The 19-year-old, who was born in Ottawa, won the first 24 matches of his college career, losing the last in the quarterfinals of the NCAA Tournament. At 5-9, 145 pounds, Levine is undersized but plays left-handed and has all the shots. He has lost his past eight matches in professional tournaments and has a ranking of No. 485, but his career is just beginning.

Audra Cohen also played her first Grand Slam match this week. Like Levine, she won only five games.

"I've never been so nervous in my life," Cohen said after losing to Andrea Petkovic. "It was the first time playing in a big scene like that -- and it showed. I doubted every ball."

One of the reasons more women than men go straight to the pros is that they mature earlier. Martina Hingis earned her first Grand Slam win at 16 and had collected four before her 18th birthday. Federer, by contrast, was nearly 22 when he got his first Grand Slam win.

Cohen, who didn't start playing tennis until she was 11, when her family moved to Florida, wasn't ready for the professional ranks coming out of high school.

"I was a late bloomer," she said. "I didn't start to play top-level tennis until I was in 18s."

As a junior this year, Cohen played No. 1 for the University of Miami. She won 42 of 44 matches and took home the NCAA singles crown. With nothing left to achieve in college tennis, she turned pro. Her ranking at the age of 21 is No. 387.

"I don't think I can ever look back and say I regret going to college," Cohen said. "Do I think I'd be sitting in a different position if I hadn't gone to college? Probably."

Donald Young, the heralded 18-year-old American, turned professional three years ago. His dismal results suggested he wasn't quite ready for the pro game. Only in the past few weeks, as he won his first two ATP-level matches, has Young looked as though he belongs.

Goldstein credits college with giving him a well-rounded experience he said has served him well.

"One thing you don't realize until you get out there is how difficult it is to cope with the amount of losing you do on the tour," Goldstein said. "If an 18-year-old has tennis as his only priority, the tour can chew you up and spit you out before you even get started. I always had other outside interests, and sometimes those distractions were a good thing."

The highest level
The competition at the ATP level can be brutal.

There are 96 players ranked ahead of Goldstein, but when he met the 2007 NCAA singles champion, it wasn't even close. Goldstein spanked Somdev Devvarman 6-4, 6-2 in the first round at Washington, D.C.

Not surprisingly, Devvarman, born in Chennai, India, and the top junior in that country, has decided to return for his senior season at the University of Virginia.

Delic also won the NCAA singles title, in 2003, but he decided to turn pro after his junior year at Illinois. He was born in Tuzla, Bosnia, and learned the game on red clay before moving to Jacksonville, Fla., at 14.

"I was happy to be considered one of the better juniors, one of the guys that could get a scholarship to go to college," he said. "At the time, I was getting beaten by Mr. Brian Gottfried, who was 50 years old at the time. Was I thinking about playing pro? No."

Delic majored in applied life studies, and after he led Illinois to its first NCAA men's tennis title, he knew it was time.

"For me, [college] was great, obviously," Delic said. "I wasn't mature enough to go out there and play. Right now, because a lot of the guys are seeing [Rafael] Nadal and [Novak] Djokovic, all these guys turning pro early, they're like, 'If they're doing it, we have to do it, too.'"

Goldstein said players who are considering a professional career should ask themselves two questions: (1) Am I prepared to have a serious impact on tour? And (2) Are the clothing and equipment people going to throw me some significant dollars?

If the answer to either question is yes, Goldstein said, go ahead and turn pro.

"By impact, I mean consistently winning Futures events, getting to the quarters and semis of Challengers and winning an occasional ATP match," Goldstein said. "By serious money, I mean more than just $25,000 or $50,000. Remember, a one-year scholarship is worth $50,000, plus coaching, tournaments and training facilities."

For Querrey, the answer to both questions was yes. He seriously considered college, but two things changed his mind. When he was invited to be a practice partner with the U.S. Davis Cup team, he discovered he had enough game to hang with the Roddicks and the Blakes. Then adidas and Prince kicked in some cash.

Despite Querrey's loss in the first round of the U.S. Open, his record this year is 19-18, impressive for someone so young. He broke through with a victory over No. 6-ranked Blake in the quarterfinals at Indianapolis in late July. Querrey has respect for Isner, who already has enjoyed great professional success after four years at Georgia.

"Hopefully," Querrey said, "more guys will start doing that. For me, I think not going to college was the right choice. I skipped college, ranked 48 right now. I can't complain. I think most likely I'll go back when I'm done."

Isner isn't quite done; he's a few credits shy of a degree in speech communication. Perhaps all the news conferences his victories have required will be considered as credit toward that degree.

He hit 144 aces in Washington, the most in a non-Grand Slam tournament since officials began compiling that statistic in 1991, and added 34 aces in his first-round match here. Isner said the strength to do it came to him in college.

"Kids playing tennis should go to college and stay there four years," Isner said. "At 17, 18 years old, they're not strong enough to compete with these 25-year-old pros."

Isner was asked about the fact that no players in the current top 10 went to college for four years. Does he wish he had turned pro earlier?

"You start playing at 21 instead of 18 -- it's tough, but it's doable," Isner said. "I have no regrets -- none at all."

When McEnroe and Connors went to college in the 1970s, most players were retiring before they turned 30. Today, with more money available and the huge advances in sports medicine, players tend to stay in the game longer than they used to. With that wider window, more players may consider college on the front end.

Ryan Thacher, America's top 18-under junior, insisted he will become one of them. He's a senior in high school at Harvard-Westlake in North Hollywood, Calif., and he already has hit balls with Pete Sampras. Still, the straight-A student has managed to keep tennis in perspective.

He turned down a wild card into the 2007 U.S. Open qualifying draw so he could go on a family vacation.

This spring, Thacher told the Los Angeles Times, "I think [college] is one of the greatest things America has to offer."

Greg Garber is a senior writer for ESPN.com.