Toronto Blue Jays prospect J.P. Arencibia has had quite an interesting baseball career – both as an amateur and a pro. The catcher tied Alex Rodriguez‘ high-school mark for most career home runs at Westminster Christian high school in Florida. He was also a star player at the University of Tennessee, which led to him being selected 21st overall in the 2007 draft as the second college backstop taken; Matt Wieters went fifth overall to Baltimore.

A year after signing, Arencibia had a breakout year at the plate. He spent the season split between high-A and double-A with a combined triple-slash line of .298/.322/.527 with 27 homers and 105 RBI. It was the second-best offensive season for a catcher in 2008 behind… Wieters. Fast-forward to September 2009 and Wieters is playing behind the dish for Baltimore, while Arencibia has packed it in for the season and is probably back home in Florida. So what went wrong for the Jays prospect?

It can be tied to his approach at the plate, or more specifically, his walk rate. Even during his star campaign in 2008, Arencibia’s rate was 4.2% at high-A and just 2.6% at double-A. His strikeout rates were 18.5% and 21.0%. In 2009 at triple-A Las Vegas, his walk rate was 5.3% and his strikeout rate was 24.5%. With his power (.200+ career ISO), the whiff rate is reasonable. The walk rate, though, is not acceptable on any level. Overall in 2009, the right-handed hitter managed a line of just .236/.284/.444 with 21 homers in 466 at-bats.

Advanced pitchers (but many of whom are not good enough to pitch long-term in the Majors) exploited Arencibia’s approach. It’s pretty clear that there is no point in throwing him a quality strike with less than two strikes. He makes Mr. First-Pitch-Swinging Vernon Wells look down right selective. Ahead in the count, Arencibia hit .298, no doubt because pitchers had to groove a fastball down the middle of the plate. His strikeout rate was 13% in that situation. Behind in the count, Arencibia hit .185 with 63 Ks and zero walks in 162 at-bats (for a K rate of 32%).

Whereas Arencibia’s value has diminished as a hitter, his defense has actually improved significantly to the point where he is considered an above-average defensive catcher. When he was drafted, there were questions about whether or not he’d be able to stick as a catcher. Prior to the 2009 draft, Baseball America stated, “The verdict is out on whether he’ll stay behind the plate as a pro. His receiving skills are rudimentary at best, and his footwork prevents him from getting off better throws despite solid-average to plus arm strength.”

This excerpt is from the Las Vegas Review-Journal:

[Arencibia] has thrown out 33 percent of runners attempting to steal (20 of 61) since starting this season by gunning down just five of 31.

“Now I’m getting respected as a defensive catcher,” said Arencibia, who often throws out runners from his knees. “I feel I’m throwing better than I’ve ever thrown, and all aspects of my defense have gotten better.”

[Las Vegas] 51s manager Mike Basso, Toronto’s catching instructor the past two years and a former pro catcher, has worked extensively with Arencibia and said he has made great progress this season.

“He’s improved leaps and bounds from last year,” Basso said. “He has done a good job behind the plate, and he’s had spurts where he’s done good offensively.

As with most of the other 2009 Prospect Duds highlighted over the past two weeks, 2010 will be a big year for Arencibia. Once considered an offense-only prospect, he has the potential to be an all-around stud if he can learn from his mistakes. It’s been suggested more than once that he has been hesitant to change his aggressive ways, but that was before his struggles in 2009. If he can get that walk rate up to even 8-9%, the impact on his other numbers could be significant.