The Rays have sucked on Fridays this year. They've compiled a 6-17 record on Friday nights, good for a .261 WPCT, while putting together a 79-38 and .675 WPCT the rest of the week. The Rays simply have performed like a different team on Friday nights.
A cursory look at their numbers, the Runs Scored and Runs Allowed totals, suggests that the Rays have been slightly unlucky with their run distribution on Fridays. The Pythagorean Win Expectancy formula allows us to get a good idea of how many games a team should've won and lost based on the runs they've scored and allowed if those runs were randomly distributed. The Rays have allowed 100 Runs and scored 79 Runs on Fridays, suggesting that they should've had a WPCT of roughly .394, or a W-L record of approximately 9-14. Still, this is a far cry from the usual day to day performance of the team. What's going on?
The opposing teams on Fridays are overall a fairly familiar group. The Rays have played 8 games against AL East rivals, 8 against sub-500 teams, and 6 against other .500 and up teams from different divisions. These teams average out to a .498 WPCT, or roughly league average. The Rays' strength of schedule is not to blame here.
How about the opposing starting pitchers? While the Rays have faced studs like Jon Lester, Josh Beckett, Brett Myers and CC Sabathia, they've also faced Nate Robertson, Jeremy Guthrie and Javier Vazquez. The Friday opponents' xFIP for the year averages out to 4.33, a total that's actually somewhat worse than the league average of 4.11. Despite this, the team has put together a clearly sub-par offense, scoring just 79 runs in 23 Friday games, good for just a 3.4 runs per game.
The Rays offense has indeed chronically underperformed on Fridays. Consider the table below:
Well, this is interesting. The team OPS drops to .596 and the team wOBA drops to .287. For those unfamiliar with the more advanced stats, BABIP is a measure of how many hits the offense lands per ball in play, while ISO is a measure of power. The offense walks a little more, but strikes out notably more and has far less power. While it appears as though the majority of the issues are from BABIP troubles, which usually aren't sustainable for a whole team, the drop in power combined with the spike in strikeouts is alarming. It appears as though something truly is making the offense worse on Fridays.
The Rays Friday struggles also extend to the other side of the ball:
This is no less surprising. The Rays pitchers get less strikeouts, walk more hitters, and give up more home runs on Fridays. Perhaps the HR/9 is something unsustainable due to a higher HR/FB, but over 200 IP the disparity is approaching statistical significance. The BABIP is roughly the same (in fact slightly "luckier") and the K and BB rates are both worse in this fairly large sample of 200 innings. Strikeout and Walk rates both stabilize fairly quickly, making this even more surprising.
These results are quite unexpected altogether. When I started this article, I was expecting something similar to this, where the results suggested that the Rays' abnormal performance was just a result of unsustainable measures being out-of-norm. Not so here. The Rays are truly playing like a worse team, and while it's obviously not as stark as the .261 vs. .675 WPCT would have us believe, there is a notable difference in the quality of the team. The distribution of at bats and innings pitched also appears to be roughly the same as usual (no pitcher has gotten more than 5 starts).
Perhaps it's just random variation but given that it's been over 200 IP and 700 PA, we might start to wonder if our players do spend their Thursday nights partying.