Lay aside the recent loss of their brightest star to injury, and the Oakland A's would seem to be in an enviable position at the moment. Right now, the A's according to the SportsLine Projection Model (@SportsLine on Twitter) have 100 percent chance of making the postseason for a third straight year and a similarly lofty 99.6 percent chance of winning the AL West for the first time since 2013. The A's current winning percentage of .625 scales to a 101-win pace across the usual 162 games. They haven't seen that kind of win total since 2002. Trouble, though, may lie ahead.
While there isn't enough time for the loss of slick-fielding, homer-hitting third baseman Matt Chapman to harm the A's all that much in the regular season, what matters is the playoffs. That's especially the case for a franchise that hasn't won a postseason series since 2006. The loss of Chapman will be keenly felt there, but that's not the only reason you should be soft-pedaling the A's as we head toward October.
Indeed, there are two reasons to be skeptical of Oakland's hopes to make a deep run that have nothing to do with the loss of one of the best third baseman in the game today. Let's have a quick look.
The A's have probably been a bit lucky, and that could change
Coming into Monday's slate, the A's were 29-17 and overseeing the largest division lead in baseball. Peer a bit more deeply, though, and the A's perhaps don't look quite as strong. Based on run differential, the A's should have been 28-18. That's not a big difference, but the divide gets wider the deeper you drill.
Over at FanGraphs, they track what's called a teams "BaseRuns." BaseRuns evaluates how many runs a team should have scored and allowed based on their underlying fundamental indicators at the batter-versus-pitcher level. At that level, the A's this season are three games worse than their actual record. "Big, large deal," you might say. "The record is what matters" That's certainly true, but things like BaseRuns often predict future performance better than actual record does, and three games is a significant disconnect across not even 50 total games. The concern isn't that the A's were 29-17 as of Monday. The concern is whether they'll play to that level going over the remainder of the regular season and into the playoffs.
One particular area ripe for regression is the Oakland bullpen. Right now, the A's lead all of MLB with a 2.21 bullpen ERA. However, in terms of FIP, or fielding independent pitching, which is scaled to look like ERA but reflects just those outcomes that have nothing to do with fielding (i.e., strikeouts, walks, and home runs allowed), the A's relief corps checks in with a mark of 3.27. That's still really good, but it's more than a run higher than their ERA. FIP predicts future ERA better than ERA itself does, generally speaking.
As well, there's what wOBA and xwOBA say about the Oakland bullpen. wOBA, or weighted on-base average, assigns proper value to every possible offensive event that happens while a batter is at the plate. Those proper valuations of singles, doubles, homers, walks, etc., distinguish wOBA from more traditional measures like AVG, OBP, and SLG. Also, for simplicity wOBA is scaled to look like OBP, which means that, say, .400 is elite and .290 is bad. xwOBA is a hitter's expected wOBA based on his quality of contact. Since we're talking about pitchers in this instance, we're referring to the wOBA that Oakland relievers have allowed this season. Anyhow, those Oakland relievers have allowed a wOBA of just .248, which is easily the lowest figure in MLB. Their xwOBA of .287 is still quite good, but it's large gap -- 39 points -- between results and expected results. Indeed, no team's bullpen this season has an xWOBA so much higher than its wOBA. The Oakland bullpen is a very good one in any context, but that's something of a red flag in the days and perhaps weeks to come.
The A's have played a remarkably weak schedule
At this writing, the A's are the only team in the AL West with a winning record. Their counterpart division, the NL West, has just two winning teams. That's notable because in 2020, teams are playing regional schedules -- 40 games against teams within the division and 20 against the corresponding interleague division. That means the A's have fattened up against some non-elite competition.
Right now, the A's have the lowest opponents' average winning percentage in all of baseball. Monday's doubleheader against the Mariners, which the A's split, pushed that figure even lower. Framed another way, the A's right now have played 48 games. Just three of those 48 games have come against teams with winning or .500 records (!). Let's state that again, for fitting emphasis:
The A's this season have played 45 of their 48 games against teams with losing records.
Those three games against winning teams came against the Padres early this month. The A's dropped two of three.
So all the above? All that stuff about how the A's have been modestly fortunate to have the record they have? That record and those somewhat weaker underlying fundamentals have been authored against a schedule that bears little relation to what Oakland will face in the playoffs and thanks in part to the peculiarities of the 2020 season is surely one of the weakest schedules in modern MLB history.
To be sure, predicting playoff outcomes in a sport like baseball is a fool's errand, but if, say, bullpen regression for the A's coincides with an uptick in the quality of competition then it could be another brief playoff stay for Bob Melvin's club. Without Chapman in tow, that risk is even more acute.