(AP Photo/Patrick Semansky)

Ronald Belisario can’t seem to get a handle on the closer role for Chicago. The 31-year-old suffered his suffered his fourth blown save of the season after allowing a pinch-hit, three-run, walk-off home run to the Orioles’ Chris Davis as the White Sox lost their fifth in a row.

“For me, it’s tough, you know,” said Belisario. “I have to get my job done, but I mean, things happen. Not lucky tonight. … I made a mistake, and I lost the game.”

Belisario hasn’t been lucky most nights – he has a 5.50 ERA in 36 innings pitched – but that should change if White Sox skipper Robin Ventura sticks with him.

Fielding Independent Pitching (FIP) measures what a player’s ERA should have looked like over a given time period, assuming that performance on balls in play and timing were league average. Belisario has a FIP of 3.17 – nearly two runs lower than his current ERA. His Expected Fielding Independent Pitching (xFIP), which is calculated in the same way as FIP, except it replaces a pitcher’s home run total with an estimate of how many home runs they should have allowed, is also lower than his ERA at 3.35. When we see these types of discrepancies despite a pitcher’s peripherals (such as groundball rate, strikeouts per nine innings and strikeout-to-walk ratio) constant with levels we have seen in the past there could be improvement on the horizon.

And that improvement could be linked to the effectiveness of Belisario’s slider. He has thrown that pitch 112 times this season, and while opposing hitters aren’t making much contact with the pitch (.205 batting average against) when they do it is usually for extra base hits (one double and two home runs out of eight hits).

Left-handed hitters have had success against Belisario’s slider down and away while right-hander have clubbed the pitch up and in.

Belisario slider ISO

“Baseball’s tough,” Ventura said after the loss. “You’ve got to put your big-boy pants on and go out there and win a game. That’s a fact.”

It is also a fact Belisario hasn’t pitched that bad, and his luck should improve enough to help win some games.