Before the season started, the Yankees were touted as having the best bullpen in the bigs. Then they lost Pedro Feliciano before he could even get going and then Rafael Soriano (a) pitched poorly; and (b) would up hurt. And things keep getting worse in that department: Joba Chamberlain has been sent to the disabled list with a strained flexor muscle.
Jay, 32, hit .296/.374/.375 in 433 plate appearances with the Cubs last season, which is adequate. He’s heralded more for his defense and his ability to play all three outfield spots.
The Mariners are losing center fielder Jarrod Dyson to free agency and likely don’t want to rely on Guillermo Heredia next season, hence the interest in Jay. The free agent class for center fielders is otherwise relatively weak.