[Falcon52]

I don't know if this guy fits the mold of what you're asking about, but I had a guy blossom when he turned 31 in to a pretty good hitter.

Some background on the guy. He was originally my 1st round pick, 12th overall a few years back. He came in with great stats, but never seemed to progress past A ball. I drafted him as an 18 year old, and he spent 6 years in A ball, never getting a ratings bump and never progressing. A couple more years pass and he no longer has a blue star rating. He turns 26 and obviously turns in to a gold star player (1 star). I decided to move him up to AAA because I do that with all gold star players, so he sat in AAA for 2 years, never really improving his ratings (I think he got maybe a bump in power, but nothing significant. Maybe going from a 41 to a 55 over his entire 10 year minor league career).

So finally, I had a lot of FA's on my big club, and decided not to resign a few and rebuild, so I brought him up as my platoon at 2b. The first year, he hit solidly. Around .280 with 7 homers and 45 rbi as the lefty part of the platoon. For two more seasons (until age 31), he batted in the .260 to .280 range and hit 5-9 homers playing the platoon. But then at age 31, he got a big bump in ratings, going from 41-55-27 to 46-65-27, and since I was still in rebuilding mode and didn't want to spend cash on a FA 2b, I gave him full time duty. He hit .276 with 22 homers and 79 rbi as a full time player. And now, at age 32, his ratings are up to 57-75-34 and in late July (about 120 games in), he's leading the league in rbi and is third in homeruns with 111 rbi and 36 homers. All in all, not bad for a guy who looked to be a bust.