Lynn, 30, missed the entire 2016 season after undergoing Tommy John surgery. He came back and had a solid year this past season, making 33 starts with a 3.43 ERA and a 153/78 K/BB ratio in 186 1/3 innings. That would seem to lay to rest any doubt about his effectiveness post-surgery, though his velocity and peripherals saw marginal declines.
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.