According to the Mariners' team Twitter feed, Pena has been added to the 40-man roster and Tacoma's Luke French--the left-hander acquired from the Detriot Tigers in the Jarrod Washburn trade--has been designated for assignment to clear his spot.
Pena is listed at 6-foot-3 and 230 pounds, but anyone who has seen the hulk of a man this season in the PCL can attest that he's likely much closer to 275 than 230.
He, of course, has otherworldly power...when he connects. But he has struck out 539 times in his big league career, meaning that 30.4% of his career plate appearances have ended via the strikeout. This season in 46 plate appearances for the Diamondbacks before his release that number was 41.3%. Small sample size, sure, but we know his modus operandi, and he is what he is.
27.2% of his minor league plate appearances have ended with a 'K', but he has put up some eye-popping numbers this season with Reno and Tacoma: 25 homeruns and a .358/.440/.712 slash in 76 games and 288 at bats.
So what does Pena offer? First off, he has already likely peaked. He isn't going to suddenly figure things out and turn into an everyday player, especially considering the park. He can't play a defensive position and will swing and miss a ton if given opportunities. But he will also run into a few and should put on some amazing shows in batting practice as well.
For a team like the Mariners starving for runs and starving for power, he could be fun to watch for a few weeks.