How The Cubs Won The NL Wild-Card Game

With a 4-0 lead, the Cubs are well-positioned to pull out the win in this wild-card game. FanGraphs win probability has the Cubs as more than a 90 percent favorite to win at the moment. But even that may be conservative: The Cubs boast one of the best bullpens in the majors (fourth by fWAR), and they will use as many relievers as necessary to get the win in this do-or-die game. It’s likely that the 90 percent win probability we currently assign them is, if anything, conservative. It should be more like 95 percent.

Jake Arrieta showed one small imperfection in his game to start the top of the fifth inning when he hit Francisco Cervelli before retiring the next three batters. During the regular season, Arrieta hit six of the 870 batters he faced, a rate of one every 145 batters. Among pitchers with at least 50 innings pitched in the majors this year, the average was one batter hit of every 119 faced. That makes Arrieta only slightly better than average in at least one pitching stat. This year there was essentially no correlation between HBP rate and the on-base plus slugging plus that a pitcher allows. That’s surprising given that a hit batter leads to a free trip on the bases, which feeds into OPS+. But we may be seeing no effect because hit batsmen are so rare, or because hitting batters is occasionally a byproduct of using the entirety of the strike zone — something Arrieta is doing well tonight.

Jake Arrieta has thrown just 47 pitches in four scoreless innings — including just 10 balls. That’s fast and accurate even by his extraordinary standards: If he maintained this pace, his pitches per inning and percentage of balls thrown would be his lowest of the season. Manager Joe Maddon kept Arrieta to just 84 and 72 pitches in his last two starts to preserve him for this game. It will be interesting to see at what point Maddon considers pulling his ace to preserve him for a likely NLDS appearance, now that the Cubs are up by four runs. The Cubs had the fourth-best bullpen by wins above replacement this year.