Shaun Marcum broke through in 2010. He finally suprassed 30 starts, albeit after missing 2009 entirely, and was a top 15 AL pitcher. With a nearly 4/1 K/BB ratio, a 1.15 WHIP, and less hits than innings pitched (in the AL East no less), Marcum showed he is ready for prime time.
Now, a year later, with the Jays in salary cutting mode after unloading Vernon Wells, Marcum finds himself a key member as a top three starter for the early season NL Central favorite Milwaukee.
Going from the AL to the NL almost always yields a substantial ERA and WHIP drop, but Marcum's differentials should be even larger given his career six+ ERA vs NYY and mid-four ERA vs the Bosox. Facing Houston and Pittsburgh has done wonders for NL pitchers ERA's for years, and this year will be no different.
The Brewers finished 14 GB of division winning Cincy last year, and a full nine games behind second place STL. The gap has been narrowed with STL simply because the loss of Wainwright should cost the Redbirds 5-6 wins off the top (not to mention the six+ WAR that Greinke adds to the Crew). Factor in Marcum and his 3.5+ WAR and you have yourself a race for the division. Hell, Marcum merely needs to maintain his K/BB ratio to go with 30+ starts and the Brewers will be in the race till the last week of the season.
The Marcsman flew under the radar last year in many regards, he didn't lead the league in wins or k's, he didn't even pitch for a third place team, but he was pretty consistent in the toughest division in all of sports and now finds himself with even less pressure, going third (after Gallardo and Greinke) to start the year.
I expect a complete repeat of 2010 for Marcum, with at least 175 k's to go with a sub 3.5 ERA and a sparkling 1.1 WHIP. Assuming he keeps his walks under 50 for the year, and he always has, the Brewers have a top three rivaling anyone in baseball, this side of the Phils. There is no team with three better righties than the triumvirate of Grienke/Gallardo/Marcum.
The Brewers have the second best offense in the NL, a top three rotation (after Phils and SF), a fantastic fan base who sells out games in September (I know because I was there). As long as the bullpen (which is question mark followed by question mark, especially when compared with Cincy's pen) holds up, the Brewers will win the division.