In the wake of of the Jon Lester signing, we’ve had a spate of articles suggesting caution about the fortunes of the 2015 Chicago Cubs. After all, while Lester is a nice little pitcher, this is a team that won 73 games a year ago, and had Jeff Samardzija performing at Jon Lester levels for the first half of the year. Or, as our friend Rob Neyer put it over at JABO this morning:

In 2015? The Cubs will need a lotta luck to challenge the Cardinals and the Pirates. In 2014, the Cubs went 73-89 and were outscored by nearly a hundred runs. In 2014, Jason Hammel and Jeff Samardzija combined for 216 2/3 innings and a 3.14 FIP with the Cubs. Also in 2014, Jon Lester pitched 220 innings with a 2.46 ERA. Not exactly but essentially, Lester does little but replace what the Cubs lost when Hammel and Samardzija were mailed to Oakland last summer. In the short term. The Cubs have also acquired Miguel Montero. Now, Montero’s better than incumbent catcher Wellington Castillo, particularly if you believe in Baseball Prospectus’ pitch-framing metrics. But it’??s not like the Cubs just replaced Drew Butera with Buster Posey or something. Castillo’??s decent, Montero’??s pretty good. In the short term, adding Lester and Montero makes the Cubs maybe two or three games better than they were last year. Or maybe I’m WAY OFF … and it’??s four or five games. Now tack on another four or five to account for the mystical powers of Joe Maddon. That still leaves them well short of scaring the Cardinals.

While I retain my fondness for Rob as a person and a writer, I think he’s a little bit off here. I think the Cubs really are contenders in 2015 now, and I think I have the data to prove it.

First off, let me start with the annual reminder that you absolutely do not want to build a 2015 forecast by starting with a team’s 2014 record and adjusting up or down to account for offseason transactions. 2014 performances are not static, and they do not carry over from one year to the next, even if the names of the players remain the same. And even if the individual performances were identical, the effects of sequencing are so large as to cause significant swings in win-loss totals.

If you absolutely have to use data from only the prior year — you never do, but just for argument’s sake — you should use a team’s BaseRuns expected record, not the win-loss mark they actually finished with. BaseRuns strips a lot of noise out of the picture, and gives a you better baseline from which to start. The Cubs expected record in 2014, per BaseRuns? 79-83, six wins better than their actual record.

Yes, they were outscored by 93 runs, but their underlying performance suggests that with the sequencing noise stripped out, they were only outplayed by about 20 runs. The 2014 Cubs, even trading their best pitchers at midseason, played something like a .500 team, and if you just reconstructed the exact same individual performances, you should expect something closer to 80 wins than 70 wins. That’s what they’re adding onto, not their 73-89 record.

But even prior season BaseRuns is problematic, because single season performances are not very good predictors of the future. The Cubs performance last year was propped up by Jake Arrieta pitching like the best pitcher in baseball, and he probably won’t do that again. Chris Coghlan hit about as well as Justin Upton’s career numbers, and he probably won’t do that again either. Kyle Hendricks isn’t going to run another 2.46 ERA. Just like we have to account for the improvements, we have to account for regression too.

And that’s why you really want your baseline to be built on a projection system. One that takes into account multiple years of data, aging curves, and current depth charts. Kind of like the one we have here at FanGraphs, thanks to the integration of the Steamer forecasts. And if you look at the updated projections after adding Lester and Montero, as well as adding in half a season of Kris Bryant at third base, this is what the projected WAR totals for the National League teams currently look like.

There’s the Nationals and Cardinals at the top of the heap, and the Pirates sitting comfortably in third place, so no, the Cubs aren’t the favorites to win the NL Central right now. But note where Chicago lies on the spectrum. Fifth place, nearly tied with the Dodgers, ahead of the World Champion Giants. In a league where five teams make the postseason, a team with the fifth most projected WAR could probably be describes as a legitimate contender.

But it’s worth noting that team WAR is not really an ideal way to project team performance. It’s an okay shortcut, but there are nonlinear interactions between teammates and run environments that WAR misses, which is why our projected standings and playoff odds reports run off the BaseRuns calculations instead. And just this morning, David Appelman has added projected BaseRuns totals for 2015 to the standings page. So let’s look at those numbers instead.

There’s some changes in the middle — specifically, the Rockies move down a bit because of their run environment — but the top five remain the same. The Nationals and Cardinals still look like the best teams in the league, with the Pirates just behind them. But then, there are the Dodgers and Cubs in a virtual tie for fourth place with the Giants. Right now, those six teams look like the class of the National League, with a step down to the Marlins beginning the next tier.

Projections aren’t gospel, of course, and there’s plenty of room to quibble here or there with some of the forecasts. Steamer loves Kris Bryant, and you could reasonably argue that the projection there is too optimistic, given that we don’t know yet how he’ll hit big league pitching or what his glove at third base might be. The team probably won’t keep both Edwin Jackson and Travis Wood around as expensive rotation depth, so maybe some of those innings will go to reserves with even worse projections.

But then again, we could play that same game on the other side of the coin. Maybe Bryant gets called up sooner than we’re projecting, and gets 600 plate appearances instead of 300. Maybe 160 innings is too conservative an estimate for Jake Arrieta. Maybe the team won’t give 1,000 plate appearances to Arismendy Alcntara and Javier Baez if they’re performing as poorly as the projections think they might. They’ll probably find an outfielder better than Junior Lake, especially now that they’ve pushed in on the short-term.

As currently built, we have the Cubs as roughly an 84 win team, five wins better than their BaseRuns mark from last year. Is that really an unreasonably optimistic forecast, given that they won’t be trading Lester and Hammel away at midseason this time around, and the kids are probably more ready for prime time than they were a year ago?

Rob is right that you don’t want to overreact to a few big offseason additions, and he’s right that the Cardinals are still the class of the NL Central. But we’ve got the projected difference between the two at four wins, and the Cubs probably aren’t done yet. If the Cardinals aren’t feeling threatened by the Cubs last 24 hours, they should be. This isn’t a great team yet, but we’re in an era where we don’t really have great teams anymore; we just have a lot of pretty good ones. And right now, the Cubs look pretty close to being a pretty good team.