(USA TODAY) -- The stitches on the elbow are long gone by the time a pitcher gets back on the mound following Tommy John surgery, and yet the stitches on the ball still don't feel right.
The patient is technically cured, his reconstructed elbow capable of allowing him to launch baseballs at the same speed as before, but in many cases he's merely a thrower, not a pitcher.
Baseball faced a startling rash of torn ulnar collateral ligaments last season, resulting in 31 major leaguers undergoing the procedure known as Tommy John surgery. That was the second-highest total ever, and twice the average of 15.8 from 2000-2011.
Now most of those pitchers are on the way back, and their performances not only figure to have an impact on the playoff races, but also on the game's overall appeal as young All-Stars like Jose Fernandez of the Miami Marlins, Matt Moore of the Tampa Bay Rays and Patrick Corbin of the Arizona Diamondbacks try to return to their old form.
And that's where it gets tricky.
GALLERY: Tommy John patients get back in the game
A study conducted last year by the American Sports Medicine Institute at MLB's behest confirmed that Tommy John surgery has an 80% success rate, as measured by a player's ability to return to his previous level of competition, usually within 12 months.
However, being back in the majors is one thing. Excelling is another. The knack for spotting a two-strike slider just off the plate or for delivering a changeup that plummets at the last moment, the skills that can mean the difference between a scoreless inning and a three-run uprising, often arrive much later.
"The ability to get control, ball movement, good placement – what makes elite pitchers elite – that's the probably the hardest thing to return,'' said orthopedist Lyle Cain, who has performed more than 1,000 UCL reconstructions and is the lead author of the seminal paper on the subject. "Because it takes a combination of control, repetition, proper mechanics and having the velocity to make the ball move like it should.''
Pitchers regularly report feeling more like their old selves the second year after surgery, making it difficult for clubs to anticipate what they can expect from their returning pitchers this season.
"When things go well, like for the 80% of pitchers, in about 12 months you're back playing pro baseball,'' said Glenn Fleisig, ASMI research director. "But you're not as good as you were until about 18 months.''
The Marlins hope Fernandez can come back as the Cy Young Award candidate he was as a rookie in 2013 before blowing out his elbow in May. The New York Mets are relying on Matt Harvey to help them return to contending status. The Oakland Athletics think Jarrod Parker and A.J. Griffin can give their uncertain rotation a midseason boost after they had the procedure five weeks apart last spring.
But there are no certainties.
"It's an art more than a science in returning to playing competitively,'' said noted orthopedist James Andrews, who does the majority of TJ surgeries to major leaguers. "There's some science, but it's still an art.''
Harvey stands the best chance of fulfilling his potential this year because his surgery took place in late October 2013, so he'll be 17 months removed from it when the season starts. That's not only preferable but closer to the new norm. More pitchers are also starting on a throwing program around the six-month mark, two months later than before.
Mindful of the future value of pitchers, especially young ones, teams have become more conservative in bringing them back.
"The trend right now, particularly at the major league level, is to make sure they're a year and a half out before we move them along competitively,'' Andrews said.
With the increase in torn UCLs, Andrews, Cain and others have turned to stem cells as a possible healing agent that could speed up the recovery process and reduce the re-injury rate, which has been climbing. Parker is among a large group of pitchers trying to bounce back from a second reconstructive surgery.
Some surgeons believe the two-time patients may benefit the most from stem-cell treatment, which is still in the trial-and-error phase, although clearly all pitchers who go through the lengthy, tedious rehab would be happy to see it go on a faster track.
Even when the recovery goes smoothly, though, the message they're increasingly getting is to resist their competitive instincts. And slow down.
"We're always reminded that even if it feels great, don't overdo it,'' Corbin said. "It's going to take time.''