NEW YORK -- His eyes red, James Blake's voice never wavered as he talked about civil rights and history and diversity.
He embraced the symbolism of starting his last tournament on the 50th anniversary of the March on Washington, an African-American tennis star inspiring young players. It was just past midnight ET when his match, and career, ended.
Blake was always comfortable sharing his rousing back story. He was also proud that his game was bigger than that.
He walked off the court at the US Open for the last time as a singles player early Thursday morning after blowing a two-set lead and losing in a fifth-set tiebreaker. The 33-year-old American fell 6-7 (2), 3-6, 6-4, 7-6 (2), 7-6 (2) in the first round to Ivo Karlovic.
Afterward, he talked about tennis but also causes dear to him. Blake has joined an organization working to end homophobia and anti-gay bullying in sports. He lamented an athletic culture "where you're too often seeing a lot of macho sort of showboating when everyone should feel comfortable."
"Sports is a great equalizer," Blake said.
He condemned the law prohibiting gay "propaganda" in Russia, which is hosting the Winter Olympics next year.
"I think everyone at this point, when you look at numbers, someone in your circle -- whether it's a family member or a friend -- is gay, transgender or bisexual," he said. "You should appreciate that those people are valued members of society, people that are doing something good in the world. They should feel comfortable to live their lives. I think any sort of policy that discriminates against them, that excludes them, is completely unfair in today's day and age. That's why I say we're 50 years out and there are still things going on that are discriminatory."
Blake had announced Monday that this would be his last tournament, ready to spend more time with his wife and young daughter. He couldn't extend his stay another round. He will still play doubles.
He rallied from down a break in the final set to force the tiebreaker but couldn't overcome the 6-foot-10 Croat's big serve at the end. Karlovic closed out the victory in 3 hours, 24 minutes with his 38th ace.
Blake threw his sweat bands, white shirt and black hat into the stands at Louis Armstrong Stadium, where the fans stayed late to try to will him to victory.
"That ovation makes me realize that everything I did, every bit of hard work, was worth it," he said in an on-court interview, his eyes welling up.
Blake had won 11 straight first-round matches at Flushing Meadows since losing in his debut in 1999. A 10-time tournament winner on the tour, he has been ranked as high as No. 4 in the world in his career and reached three Grand Slam quarterfinals.
"I'm proud that I have the rest of my career to look back on as some pretty good matches, some pretty good wins," he said. "Hopefully this won't be my lasting memory, is that loss, up two sets to love, two tiebreakers in the fourth and fifth, losing both of those. Pretty much in my hands at times, and I was the one that I felt like I gave them away."
Blake ended his career 4-15 in five-set matches.
"I definitely won't sleep a whole lot tonight," Blake said. "I'll be thinking about opportunities I had."
Karlovic hadn't been any better -- he went in 3-13. His one previous comeback from down two sets? It also was against Blake, at the 2009 Davis Cup.
The 34-year-old Croat has been ranked as high as 14th but had to qualify for this year's US Open. He will next face ninth-seeded Stanislas Wawrinka.
Earlier, Juan Martin del Potro overcame delays from the rain and his opponent to pull out a grueling four-set win in the first round.
The 2009 champion was frustrated by 74th-ranked Guillermo Garcia-Lopez's repeated calls for a trainer to work on his left leg. Del Potro, seeded sixth, rallied from a break down in the last set to win 6-3, 6-7 (5), 6-4, 7-6 (7) in 4 hours, 13 minutes.
"I think of all of the matches of the first round, I had the toughest one," del Potro said.
Del Potro had match point at 6-4 in the final tiebreaker when Guillermo-Lopez blocked back a serve into his body, and the ball somehow landed near the line. Just as it was called out, del Potro hit an easy chance at a forehand winner into the net.
Garcia-Lopez challenged the out call, and it was overturned on review. The chair umpire ruled that the point should be replayed, but Garcia-Lopez argued that he should have been awarded the point.
He went on to win the replayed point, anyway, then saved two more match points before del Potro finally won with an emphatic backhand winner. He pumped both fists and bellowed, relieved at the end of a long day.
Garcia-Lopez upset 10th-seeded Juan Monaco in a fifth-set tiebreaker in the first round at Flushing Meadows last year. He proved a pest again Wednesday, running down shot after shot.
"We play every time long rallies," del Potro said. "I got to make three or four winners in the same point to win the point."
More than four hours of rain delays during the day meant 2012 champion Andy Murray did not play his first point of the tournament until 9:55 p.m. ET, making for the third-latest start to an Open night session.
Murray wasted little time reaching the second round, playing nearly flawlessly during a 6-2, 6-4, 6-3 victory over Michael Llodra.
Murray, who is seeded third, made only five unforced errors, while compiling 34 winners in the 1-hour, 38-minute match.
No. 17 Kevin Anderson of South Africa, No. 20 Andreas Seppi of Italy, No. 21 Mikhail Youzhny of Russia, 2001 US Open title winner Lleyton Hewitt and 109th-ranked American wild-card entry Tim Smyczek also were among the winners. No. 16 Fabio Fognini and No. 29 Jurgen Melzer lost.
Information from The Associated Press was used in this report.