Why did Flores favor his fastball?

In the bottom of the 11^th on Saturday night’s tryst with Cleveland, Ron Gardenhire summoned left-handed specialist, Randy Flores, out of the pen and deployed him to dispose of the Indians’ two high-profile lefties in Shin-Soo Choo and Travis Hafner. Only Flores, the pitcher claimed off the Rockies roster in August to specifically retire left-handed opponents, failed to meet his job description. 

Favoring his fastball, Flores allowed back-to-back singles by Choo and Hafner and quickly put the Twins in jeopardy of potentially losing two consecutive games to the lowly Indians. Only a well-concocted and executed defensive play combined with Matt Guerrier’s pitching saved Flores from being responsible for allowing what would have been the winning run to reach base.

According to La Velle E Neal, the manager took exception to Flores’s decision to throw fastballs to the left-handed pair rather than his slider. “If I wanted a fastball thrown I would have put a right-hander in,” commented Gardenhire. La Valle continued by saying:

A White Sox scout here said [on Sunday] that all the scouts in the stands were wondering the same thing. Twins catcher Joe Mauer was calling for breaking balls but Flores was shaking him off. Flores told Gardy that he had been giving up hits off his breaking balls lately.

When thrown effectively, sliders will break out of the zone down-and-away from opponents and incite either empty swings or weak contact on out-of-zone balls. By not having the confidence in his slider to throw it to Choo or Hafner, Flores made the admission that his ability to retire hitters has greatly diminished. Since his acquisition he’s only been asked to take care of 13 batters, eight of which were left-handed. Of the eight, he has now only successfully retired one.

What was Flores's reasoning behind not throwing a slider (or curve for that matter) under those circumstances to Choo and Hafner?

"We talked about it,'' Gardenhire said. "He told me he was being really stubborn because he's given up a couple hits on breaking balls. So he went out there and was stubborn."

Admittedly, Flores does have an acute self-awareness as his last three sliders that have been put into play have resulted in hits. Left-handed opponents are slugging .615 against his slider this year as well – the second-highest mark among southpawed relievers – so his decision to shake off Joe Mauer has merit. Meanwhile, same-sided opponents have slugged just .333 off of his fastball. Then again, even with that sort of logic, this behavior does not appease the manager:

"That's really overthinking," Gardenhire said. "He really wants to be part of this and do his job but you can't overthink these things."

When the Twins picked up Mahay from the Royals late last year, the first thing they did was convince him to throw his slider more frequently. Mahay went from dishing out his slider just 19% of the time while in Kansas City to chucking it 32% of the time in Minnesota. Not surprising, his batting average allowed dropped from .321 to .216. Unlike Mahay, whom the Twins were successful at persuading him to throw his slider regularly, Flores does appear completely onboard with this policy.

Of course, not throwing this pitch would make him an outsider among the bullpen ranks as the Twins relievers serve up more sliders than your standard White Castle. Among the 32 teams, Minnesota’s bullpen tosses sliders 28.2% of the time – the second most in baseball behind the Chicago Cubs. Dating back to 2005, the Twins have been at the top of the league in amount of sliders thrown. Clearly, this is a philosophical decision to have relievers that favor this type of pitch. Which is presumably why Gardenhire was upset over Flores's decision to shake off Mauer: The Twins have a gameplan and would like their pitchers to execute said gameplan.

What’s more is that it works for them. Using Fangraphs.com’s Pitch Value total (more information on that statistic here), the Twins’ relievers are 35.8 runs above average when throwing their sliders which is the best in baseball. This is an outstanding figure, meaning that the Twins are retiring a lot of their opponents when using this pitch. But for his part Flores has been a detriment when throwing his, contributing -1.2 runs to the total when throwing his slider since coming over to the Twins.

Needless to say, this appearance and the ensuing response from the manager may have a seriously negative effect on the 34-year-old lefty. With left-handers Jose Mijares and Brian Fuentes both returning from injuries and both being better options to retire lefties, Flores’s window opportunity to demonstrate that he can be useful component on the team’s playoff roster may have closed on Saturday night.