In 2007, Cleveland Indian lefty, Cliff Lee had an ERA of 6.29 and WHIP of 1.521. He won only 5 of the 16 games he started, gave up 36 walks and 17HRs in 97.3 innings.
In 2008, Cliff Lee had an ERA of 2.54 and a WHIP of 1.110. He went 22-3, pitched 4 complete games, gave up 12 HRs—5 fewer than in 2007 despite pitching 126 more innings—and only 34 walks. Needless to say, Lee is a favorite for the AL Cy Young.
Lee says last year's disaster prepared him for this season. "I got hurt in spring training last year and that had quite a bit to do with my rough season. But sometimes going through some failure makes you a better player in the long run."
Cases for most surprising player could be made for others; Carlos Quentin came from Nowheresville to claim 2nd in the AL for slugging percentage, 4th in OBP and to lead the AL in HRs per AB, averaging a dinger every 13.3 at-bat. Ryan Ludwick more than doubled his career high of 52 RBIs and came in 2nd in the NL to teammate Albert Pujols with a .591 slugging percentage. And nobody on the planet—including Josh Hamilton himself—expected the year he had; 130 RBIs, 190 hits and an OPS of .901.
However, Lee's transformation was singular. After geting shelled through July and a demotion to AAA last July, Lee was left off the postseason roster. Then over the off-season, Cleveland tried hard to shop Lee around, (ironically, almost acquiring Carlos Quentin for him) but found no takers, getting rejected by the Pirates, Cardinals and D-Backs. This spring, Cleveland told Lee he'd have to earn the number 5 rotation spot against Jeremy Sowers and Aaron Laffey.
Lee responded by leading the AL with a 2.54 ERA, starting the All-Star game and winning 22 games. For those reasons, the case should be clear; Cliff Lee is the most surprising player in the MLB this season.