Most of the risk used to involve losing the negotiating leverage of that final year of college eligibility, but the precedent has been broken more than once in recent drafts.
The Chicago Cubs, for instance, picked South Carolina's Landon Powell in the sixth round in the 2003 First-Year Player Draft. He returned to school, developed into one of the best catchers in the 2004 draft, and was taken by the A's with the 24th overall pick.
For Powell, staying at South Carolina was a great business decision. He earned a $1 million signing bonus, far more than he would have received as a sixth-rounder. Many of this year's best college seniors stayed in school for the same bottom-line reason.
"I thought I had a really good chance of going higher last year, and things didn't work out," said Randy Boone, a right-handed reliever with the University of Texas who was selected by the Minnesota Twins in the 22nd round. "I placed a value on my senior year at Texas, and unless someone could eclipse that value, I was going to come back."
The Twins didn't, and Boone returned to Austin. The Toronto Blue Jays couldn't lure its 22nd-round pick, Arizona right-hander Brad Mills, out of college, either. But Mills says he balanced his draft value with his college education.
"I'm a civil engineering major, and it isn't the kind of thing that I can take five or six years off to play ball and pick right back up if I had to," said Mills. "It would take a lot of extra work for me to do that."
Other top college seniors had more philosophical rationales.
"I had just come on late in the season and was finding out who I was and how to pitch," said Vanderbilt closer Casey Weathers, recalling his thoughts when the Detroit Tigers selected him in the 25th round last year. "I didn't feel like I was ready. I felt like I had more to do at the college level. It was a pretty easy decision, actually."
Weathers also liked Vanderbilt's chances of reaching the College World Series, similar to the reason why North Carolina right-hander Robert Woodard decided to spend his senior year back in Chapel Hill after St. Louis picked him in the 45th round last summer.
"With the guys we brought back, I thought we had a very good chance to make another run for the championship," said Woodard, whose Tar Heels narrowly lost to Oregon State in last year's College World Series final. "If I didn't feel like the pieces were in place, I probably would've signed with the Cardinals. But we have a good shot at doing it again. As a lifelong Tar Heel fan, there would be nothing better than winning a College World Series title here."
But perhaps the most philosophical of the bunch is Florida slugger Matt LaPorta, who entered his junior year as a certain first-round pick after having a huge sophomore year for the Gators. An oblique injury led to a subpar season, however, and LaPorta fell to the Boston Red Sox in the 14th round.
"It was a tough decision, but at the same time, the process wasn't that bad," said LaPorta. "I sat down and said a few prayers and thought God was leading me to come back to school and help this young team out this year."
In the process, LaPorta helped himself quite a bit. After hitting just .259 in 2006, the slugger was hitting over .400 with a week to go in the regular season, and he was leading the Gators in home runs for the third straight year. There is little doubt he has improved his draft stock.
"I've gotten better at every aspect of the game," he said. "The biggest improvement I've made is with my strike zone discipline. I don't swing at anything out of the zone, which has been a key to my success so far."
Obviously, LaPorta doesn't regret returning for his senior year, nor do many of the other college seniors in this year's draft.
"I've made lots of strides mechanically and cleaned up a few things," said Weathers, who was 9-2 with a 1.49 ERA and five saves by mid-May. "My command is better and my slider is tighter. There are a lot of things that have improved. I didn't have anything going for me last year, except a decent arm."
"I'm thankful for the opportunity to come back and my play senior year," added Boone, who had 58 strikeouts and just eight walks in 59 1/3 innings of work for the Longhorns. "It's been cool to go through everything knowing it'll be last time I'll experience it. It's sort of been like a farewell tour."
Another perk is knowing what the draft will bring. Many of the seniors say the biggest thing they got from the experience is learning how unpredictable it is.
"I can only control how I prepare and compete on the field," said Woodard. "If I'm the last pick of the draft, that's where I go. I told myself before the season started to do everything I can to prepare to pitch and help the team win, and I think I've been able to do that."
There's little doubt that Woodard and the other seniors hope their risks pay off in the end, however. Their final year of college will be all the sweeter if they go early on draft day.
Chris Gigley is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.