But despite all of his flaws, which includes striking out in nearly a third of his major league at-bats, the veteran slugger has always possessed immeasurable power.
Pena hit 26 home runs as a 22-year-old kid with the Cincinnati Reds in 2004, giving fans their first real taste of his Herculean power. He followed up with 19 in 29 less at-bats in 2005, but also struck out 34.6 percent of the time.
So when the Red Sox traded pitcher Bronson Arroyo for him before the start of the 2006 season, it was seen as a roll of the dice by Theo Epstein and Co.
In his first season with the Sox, Pena showed some promise. He hit 11 blasts in 84 games but, more importantly, he set career highs in batting average (.301) and on-base percentage (.349) as the team's fourth outfielder behind Manny Ramirez, Coco Crisp and Trot Nixon.
But while Pena seemed to look like he was on the verge of becoming a full-time major leaguer, there were still some idiosyncracies that were troublesome.
He swung at 35.8 percent of the pitches thrown to him outside the strike zone with the Sox in 2006 — a rise of nearly six percent from the previous season and a rise of 13.1 percent from the season prior to that.
So when pitchers began feeding Pena a heavy dose of offspeed stuff outside the zone, particularly the following season, when he saw the least amount of fastballs (percentage-wise) he had seen in his major league career, it was a recipe for disaster.
Then, when you take into account Pena's relative lack of speed and mediocre defense, it was only a matter of time before not only Pena's Red Sox career was over, but his entire big league career was over.
Sure enough, on Aug. 17, 2007, the Sox shipped Pena and his still-untapped potential to the lowly Washington Nationals for a player to be named later — which ultimately translated into Chris Carter.
Less than one year later, Pena was out of the big leagues, never to return — or so we thought.
The 6-foot-3, 230-pounder has come out of nowhere this season to jack five blasts in 46 at-bats with the D-Backs. And while he's still showing a lot of the old tendencies that did him in the first time around, he's also showing off what captivated us in the first place — that amazing, raw power.
While 46 ABs is an extremely small sample size, it's tough not to be awed by his 62.5 percent home run/flyball ratio on batted balls in play. The major league leader in that category (among players qualified) is Lance Berkman, who leads the NL in home runs, at 27.9 percent. Jose Bautista, the major league home run leader, ranks second at 27.4 percent.
Obviously, Pena's number should dip with more at-bats. But it's still a major indication that the surplus of power he was once highly touted for is still there.
Then again, why shouldn't it be?
He's still only 29 years old, the age that Jose Bautista was last season when he turned into an MLB superstar with a major league-leading 54 home runs.
Now, is Wily Mo Pena going to suddenly blossom into a big league star? Probably not.
But he could have at least blossomed into a Home Run Derby star had he been given the opportunity to participate on Monday night by NL captain Prince Fielder.
Fielder said after making his selections that he had wanted to include an Arizona Diamondback, with the event taking place at Arizona's Chase Field. The most obvious candidates were Chris Young and Kelly Johnson, who lead the team with 16 home runs each, and Justin Upton, the team's budding superstar.
But if Fielder dug a little deeper, he would have seen that what the event really needed was a little bit of Wily Mo Pena. Everything just seemed to fit.
Pena has that batting practice, all-or-nothing swing, which is intriguing in and of itself when it comes to the home run contest.
Then, there's the added hometown factor. The fans at Chase Field would have loved to have seen one of their own swing for the fences on the eve of the Midsummer Classic.
When you sprinkle on top of that the fact that Pena has come out of nowhere during the three weeks leading up to the event, after two-plus years in Triple-A, it couldn't have been an any more perfect setup.
Baseball fans would have loved to have seen what Pena could do in a competiton like the Home Run Derby. But more importantly, casual fans, who the event is mostly geared toward, would have been given someone to root for — a hometown, feel-good underdog.
Perhaps Wily Mo would have failed to live up to the Home Run Derby hype just as he did during his major league career. But either way, Prince Fielder swung and missed before even taking a cut on Monday by not including the veteran slugger.
