GAINESVILLE, Fla. -- When Florida coach Urban Meyer walked out of his office around noon Wednesday, he saw starting guard Maurkice Pouncey wearing a sling on his right arm.
Down the hall, promising sophomore fullback Steven Wilks was standing on crutches, having torn the anterior cruciate ligament in his left knee in practice two days earlier.
"It's the worst part of coaching," Meyer said.
The best part of coaching came a few months ago. When 2007 Heisman Trophy winner Tim Tebow announced Jan. 11 that he was returning to Florida for his senior season, the Gators once again became the team to beat.
Even if Tebow had entered the NFL draft, defending national champion Florida might still have been ranked No. 1 in preseason polls. The Gators return all 11 starters on defense, including Brandon Spikes, possibly the best linebacker in college football. In fact, Florida brings back all 22 defensive players from last season's two-deep depth chart.
But during the past month, Meyer has learned how fragile a team's championship hopes can be.
Nearly a dozen projected starters have been sidelined during spring practice, and many will miss Saturday's Orange and Blue spring game at Ben Hill Griffin Stadium. Key defensive linemen Lawrence Marsh and Carlos Dunlap were the latest casualties, as each player underwent abdominal surgery Wednesday.
Other than Wilks' knee injury, most of Florida's injuries haven't been catastrophic. Most players will return for voluntary offseason workouts, and nearly all are expected back before the start of preseason camp late this summer.
But Meyer doesn't like that his team hasn't been able to hit and scrimmage during spring practice as much as he had hoped. On Wednesday, the Gators practiced in shorts and helmets even though they could have worn pads under NCAA rules.
"There are three things that can derail a really good, experienced team," Meyer said. "The first is getting soft and losing your edge. [Florida basketball coach] Billy Donovan talked about it all the time with his teams, how they never lost their edge and were always hungry. Discipline is the second thing that can hurt you. If we have discipline issues and guys aren't here, that can really hurt you. The third thing is injuries. If we can eliminate those things, we'll be pretty good."
So far, at least, the Gators have avoided the first two pitfalls as they begin their quest for their third national championship in four seasons. Florida's players largely have avoided off-field problems compared to the past two offseasons, and Spikes and Tebow seem determined to keep their teammates hungry.
"Yeah, we've got a lot of returning starters, but we've just got to keep grinding, keep getting better," Spikes said. "The success we had last year was last year. People aren't going to care about none of that this upcoming season. We're going to have the target on our backs, and we know that. It feels good to know you're returning all those starters. But if we don't do all the small things we did in the past, it can all go down the drain. The national championship's not going to win any games for us next year."
The Gators learned the difficulties of defending a national championship in 2007. After beating Ohio State 41-14 to win the 2006 BCS national championship in Meyer's second season, Florida finished 9-4 the next year.
Meyer said this upcoming season will be different.
After Florida blasted the Buckeyes to win its second national championship in football, four underclassmen entered the NFL draft, including All-American safety Reggie Nelson and defensive end Jarvis Moss. Quarterback Chris Leak was a senior, along with many of the pieces from one of the best defenses in the country.
Meyer doesn't have to worry about finding leaders this fall. Nearly everyone is back from last season.
"It's apples and oranges [compared to 2007]," Meyer said. "It's a complete 180. We're just better. There were a multitude of issues with that  team. Last year was the most professional team I've ever been around as far as how they handled their business. We can't lose that."
Tebow already is trying to make sure that doesn't happen. Pouncey said that after the Gators beat Oklahoma 24-14 to win the 2008 BCS national championship, Tebow didn't wait long to remind his teammates how poorly their last title defense had played out.
"Tim always says we don't want to have a season like we did in '07," Pouncey said. "If we see someone slacking off, we tell them we have to work harder. We lost a lot of leadership off that first team. We don't want to have it happen again. We're going to go out with the same edge and try to beat everybody."
Even with so many starters back, the Gators aren't standing still. New quarterbacks coach Scott Loeffler, who worked with Chad Henne, John Navarre and Drew Henson at Michigan, is tinkering with Tebow's throwing motion. Tebow also is working under center a lot more after playing out of the shotgun the past three seasons. And Meyer said he's determined to get sophomore John Brantley more snaps this fall as the Gators prepare for the post-Tebow era.
"I'd like to get him in the first quarter of every game," Meyer said. "I don't know if it will happen. But the best news of all is he's earning that chance right now."
As good as they were a year ago, the Gators know they'll have to earn another trip to the BCS National Championship Game.
And, of course, they'll have to avoid the injuries that have plagued them this spring.
"We have a target on our back every week to go out there and play like we know we can," safety Ahmad Black said. "Everybody wants to beat us. Everybody wants to take down the champ, but they've got to go out and do it."
Less than five months before their Sept. 5 opener against Football Championship Subdivision opponent Charleston Southern, Spikes said the Gators are ready to begin their defense.
"Our biggest thing is not getting complacent," Spikes said. "When you've got two national championships already, it's easy to get satisfied. We've got All-Americans on this team, guys with All-SEC honors. It's easy, man. You say, 'What else can I do?' But nothing beats winning a championship."
Mark Schlabach covers college football and men's college basketball for ESPN.com. You can contact him at firstname.lastname@example.org.