In keeping with history, but not without good reason, it’s the Boston Red Sox who are causing the most fretting among Yankee fans. This season, however, the Toronto Blue Jays have positioned themselves as a third legitimate contender in the American League East. Currently, the Jays are only two-and-a-half games out in the East, only four games back in the AL Wild Card chase, and only one game behind New York in the wins column. The question, then, is: Are the Blue Jays for real this season?

To begin to answer this question, let’s turn to something called the “First-Order Standings” available at Baseball Prospectus. First-Order Standings measure what teams’ records should look like based on their runs scored and runs allowed on the season. Here’s how this year’s AL East looks in first-order terms:

As you can see, the first-place Red Sox drop to third in the First-Order Standings, and the Yankees find themselves two or so games ahead of the Jays. That’s because the Yankees’ run differential (+66) and the Jays’ run differential (+36) are measurably better than Boston’s (+25). As strength of schedule goes, the Blue Jays have played the third-toughest docket of opponents in baseball, an average opposing winning percentage of .511).

Overall, the Blue Jays’ strength has been their offense: They rank third in the AL in runs scored behind only the Yankees and Indians. The Rogers Centre, where Toronto plays its home games, is a hitter’s park, but not so much that it significantly dampens what the offense has accomplished to date. More specifically, the Jays’ strength has been power. They lead the AL in slugging percentage (.495), home runs (89), doubles (132), and total bases (1,069).

On an individual level, the Jays are getting big numbers from a number of key players. Veteran centerfielder Vernon Wells and third-year breakout star Alexis Rios are both on pace to tally more than 90 extra-base hits, while Troy Glaus and Shea Hillenbrand are on target to combine for 81 homers. Then there’s Lyle Overbay, who’s slated for 30 doubles and 24 bombs.

Of those, only Rios has grossly overperformed to date. Entering the season, Rios was a career .273 AVG/.321 OBA/.390 SLG hitter, and, accordingly, Baseball Prospectus forecast that Rios would put up a modest batting line of .277/.328/.434 with 11 homers when the season began. It’s now mid-June and Rios has already hit 12 home runs and authored a gaudy .338/.379 /.600 batting line. That high – and possibly aberrant – batting average means Rios is likely to regress as the season wears on, but he’ll still comfortably exceed expectations. Newcomers Glaus and Overbay, meanwhile, are making the Jay’s front office look very good.

As the pitching and defense go, the Jays rank eighth in the AL in runs allowed. The rotation, fronted by 2003 AL Cy Young winner Roy Halladay, has a cumulative ERA of 4.88 – good for seventh in the AL – while the bullpen ERA of 4.90 ranks a paltry 11th in the junior circuit. Elsewhere, the Jays place a respectable third in the AL in Defensive Efficiency, a measure of what percentage of balls in play get converted into outs.

The success of the rotation, of course, depends on keeping Halladay healthy (he made three trips to the disabled list from 2004-05). On the upside, A.J. Burnett recently began a minor league rehab assignment and is slated to rejoin the big league rotation on June 22. He was struggling before he went down on April 21 with a sore elbow, but Burnett’s history of high strikeout rates in tandem with strong groundball tendencies bode well for the future. Of course, as with Halladay, he needs to stay healthy (five DL stints since 2000).

In the bullpen, closer B.J. Ryan has been outstanding (according to Baseball Prospectus’s Relievers Expected Wins Added, only Jon Papelbon has been the better AL pen man this season), but the middle-relief corps leaves much to be desired. Remove Ryan’s numbers from the mix, and the Toronto bullpen ERA climbs to 5.64, clearly indicating a weak spot.

Long-term, the Jays figure to see some decline from Rios, but if Burnett is able to cobble together a healthy three-and-a-half months, the loss in runs should be offset. GM J.P. Ricciardi will need to be creative at the deadline in order to bolster the pen, but fortunately for him, it’s not difficult to scare up useful middle relievers before July 31. Specifically, the Jays badly need another reliable righthanded setup man to aid Justin Speier in the middle innings.

At a base level (i.e., runs scored and runs allowed) the Jays have cause to think they’re better poised than Boston long-term, and that’s certainly a new scenario in the East. Given the Red Sox’ pitching uncertainties and the Yankees’ injuries, the Jays could find themselves in the playoffs for the first time since 1993. But it’s going to take health and an active and focused deadline by Ricciardi and the Toronto braintrust.

Mr. Perry is a writer for Baseball Prospectus. For more state-of-the-art analysis, visit www.baseballprospectus.com.