Players change all the time, and my opinions need to change with them. A player might get stronger or weaker, might change his mechanics, might acquire a new skill, or he might not change at all - I may have just come up with an incorrect evaluation. Here are five notable big leaguers who have shown themselves to be better than what I projected for them coming into the 2012 season.

Gio Gonzalez, LHP

I was never a Gio fan when he was coming up in the minors for two major reasons. One, every time I saw him, he was working with a fringy fastball -- down in the 86-88 mph range in one outing, and never above 91. The other, and the bigger concern, was that he wasn't just a guy with fringy control, but had a tendency to see his control and command disintegrate in tough situations, such as when a fielder behind him failed to make a play. Even last year, sources of mine who knew or saw Gonzalez indicated this was still something of an issue, just that his raw stuff had improved enough to allow him to overcome it.

While Gio still does things that concern me -- too many walks, allowing too many balls hit in the air -- that meltdown potential hasn't been there in games, and his stuff continues to miss bats, more than ever thanks to the switch in leagues. He's a solid No. 2 starter for just about any club that doesn't have a Stephen Strasburg/Jordan Zimmermann combo up top.

Jon Jay, CF

I first saw Jay when he played for Team USA in 2005, where he was primarily a corner outfielder due to the presence of Drew Stubbs, a plus defender in center, on the roster. Jay had a solid if somewhat linear swing that generated line drives but not power, and he never showed me the kind of approach or patience that would indicate he'd be a high-OBP hitter, so he'd have a hard time profiling as an everyday player in a corner because he didn't have the secondary skills.

Two things have become clear about Jay since he first arrived in the big leagues. One is that he's become an average defender in center, an improvement even over where he was in 2010, and a big leap over where he was coming out of college. The other is that even without patience or power, he can make enough line-drive contact to keep his batting averages high -- a career .301 average and a career .348 BABIP -- and thus make himself an above-average player overall. He will probably have a year where he runs into some bad luck on balls in play, but in years where he hits .300 and plays average defense he'll be worth at least 3 wins above replacement.

Josh Reddick, RF

I pegged Reddick as an extra outfielder when he was traded from Boston to Oakland last winter because his plate discipline was so poor that there seemed to be no reason for pitchers to throw him hittable strikes. He has bat speed and the loft in his swing for power, but there's a popular (and well-founded) scouting axiom that you can't hit for power if you can't hit.

Reddick has hit and walked just enough this year -- he ranks 60th in the AL of 83 qualifiers in both batting average and OBP through Sunday -- to get to his power, which has also proven to be more than I expected, even producing power in Oakland's pitcher-friendly park. He's also been an excellent defensive outfielder in right. One small red flag here: While he's become more patient, he's still below-average in that regard, and is more likely to fall behind in the count than the typical AL hitter this year, so he's probably dancing on the edge of what's required to let that raw power come through.

Jeff Samardzija, RHP

Had you asked me my opinion of Samardzija after last season -- and it's probably telling that no one really did -- I would have said he was just a middle relief candidate, and someone who'd probably be traded or non-tendered once he started to get expensive. He showed up in spring training this year with a cleaner delivery that allowed him to improve his command of everything he threw, and would flash an improved split-change and/or slider depending on when you saw him. (He was better, but not great, when I saw him in late March.)

Over the course of the season, Samardzija was similarly inconsistent, but at times looked like an ace, driving the ball down in the zone, getting the slider and/or cutter in under left-handed hitters' hands or at their back feet, showing good arm speed on the changeup. If he can bring that arsenal and command to more and more starts, he could be a No. 1 or 2 starter, with the latter a much more likely outcome.

Doug Fister, RHP

When the Tigers acquired Fister last summer for four young players, none an elite prospect, I thought they'd overpaid for a back-end starter who'd benefited from a great ballpark and great defense in Seattle, which is what Fister was for his first two years in the majors.

This year, however, Fister's curveball has become a legitimate out pitch for him, 74-76 with a severe, late-appearing vertical break, right off the table, so even with some loss of velocity (probably due to a strain to a rib muscle on his left side) this year he's been able to increase his strikeout rate. He also has been throwing more two-seamers to generate ground balls, a change that dates back into 2011. The improved breaking ball this year is huge for him, but the two-seamer and the plus control were already there at the time of the trade, something I should have weighed more heavily when Detroit made the move.