The numbers are very rough and based on some wild assumptions for rookies and younger starters.
In 2012, the Blue Jays' starting rotation was, um, shall we say, ugly. We watched three out of five starters go down in the span of a week (two of them to Tommy John surgery) in June. We saw Ricky Romero, the "ace" of the rotation implode as he lost his command and batters stopped swinging at his offspeed stuff (curve and changeup). By the end of the season, the Jays had one good starter (Brandon Morrow), one decent starter who flagged at the end of the season (Carlos Villanueva, now a Cub) and a cast of thousands understudies. As a group they were terrible by every measure from old school stats to sabermetrics.
In this article I look at the possible 2013 rotations. I am going to use bWAR (Baseball Reference's version of the Wins Above Replacement statistic) for the sake of my ease (and familiarity with Baseball Reference scripts) and the fact that bWAR is friendlier to knuckleball pitchers.
Let's look at the team pitching first.
From Baseball Reference (bWAR)
Sorting teams strictly by bWAR with all Playoff Teams in BOLD.
As you can see, the San Francisco Giants had the worst pitching staff of all the playoff teams but they were the World Series Champs, so one can imagine a chorus of math hating journalists singing "WAR what is it good for? Absolutely Nothing!!" Funny enough, the Jays were only 0.5 bWAR behind the Giants (and 0.4 bWAR behind the putrid 55-107 Houston Astros), but the Giants were light years ahead of Toronto because for the most part their starters were healthy.
What should really stand out is that 7 of the top 10 teams in team pitching bWAR made it to the playoffs.
Note: although the above team bWAR values are for the entire pitching staff, I will only look at the starters for each team in the American League East.
A.L. East Rotations (Ordered by 2012 Standings)
Here are the projected rotation results based on each team's top six starters with projected bWAR based on the last 3 seasons (weighted 5/4/3 of their last 3 seasons) with a -0.5 bWAR reduction for any pitcher older than 31 years old. For younger pitchers, I upped their numbers based on the very wild assumption they will make incremental improvements and for rookies they would maintain their numbers.
Total Projected Starting Staff bWAR = 14.03
The Yankees rotation is heavily dependent on older pitchers. If they lose CC or age catches up to both Pettitte and Kuroda then the Yanks are in trouble. Might be offset if the younger pitchers breakout (especially Nova.)
Total Projected Starting Staff bWAR (with Saunders) = 9.02
Total Projected Stating Staff bWAR (with Arrietta instead of Saunders) = 7.96
The Orioles' starting staff was the weakness of the team last year. If they don't get some innings and improvement from their starters (plus Hamels and Chen maintain or improve and not fall back) next year then the Orioles may find it hard to compete especially if their BP doesn't perform at the fantastic level they did last year.
Total Projected Starting Staff bWAR =11.55
Also shows how much losing Shields hurts the Rays. Their rotation will be much better if Moore, Niemann, Archer and Cobb can step it up this season.
Total Projected Starting Staff bWAR = 14.53
Shows how much the trades improved Toronto's rotation. The top 3 starters weren't even with the Jays at the end of the 2012 season. The key to success is always health (sigh), Dickey doesn't turn into a pumpkin and a return to form by Ricky.
Total Projected Starting Staff bWAR =7.50
Based on bWAR projection, the weakest rotation of the AL East. For the Red Sox to be successful they are going to need major improvement from all their pitchers. If a single one falters then the Red Sox are in for some disappointment. More than one stink it up then the Red Sox are in trouble.
Best Rotation in the AL East
Baltimore (Pixie dust is forever!) (3 votes)
Boston (John Farrell will make them whicked good) (23 votes)
New York (Old? Whatsamadda wit ya!) (41 votes)
Tampa Bay (Stupid 2%) (97 votes)
Toronto (Just because) (578 votes)
742 total votes