Sabermetrics, the advanced stats that best explain the quantifiable aspects of baseball, have never been a fan of Ivan Nova. Every advanced stat out there showed that in 2011, Nova’s 16-4 record and 3.70 ERA were not an accurate representation of his worth as a pitcher. From a relatively low BABIP (.283) to an xFIP of 4.16, Nova projected as a back-of-the-rotation guy, not a top-flight starter.

Nova picked up where he left off in the beginning of this season, putting up pitching results that again overinflated his relative value. But most fans don’t check BABIP, xFIP, and the rest of the alphabet-soup advanced stats with their morning coffee — they look at wins, losses and ERA. The casual baseball fan is much like my father, who will swear up and down that C.C. Sabathia got jobbed out of the 2010 AL Cy Young award by Felix Hernandez because C.C. was 21-7 and King Felix was 13-12.

Those same fans pointed to Nova’s 9-2 record in late June as evidence that his 2011 campaign was no fluke. But as Grantland’s Jonah Keri explained in an eerily prescient June 12 column, Nova’s success was still primarily a product of luck.

Nova’s official rookie season in 2011 was a year-long testament to good fortune. The Dominican right-hander posted one of the worst strikeout rates for any starter last season at 5.3 per nine innings. He wasn’t particularly stingy with walks, surrendering 3.1 free passes per nine frames. But he also pitched for the Yankees, which has its benefits. The Bombers scored an incredible 8.8 runs per game for Nova last year, second behind only Derek Holland’s 9.2 runs of support per game. That’s how Nova went 16-4 on the season despite lousy peripheral stats, and that’s how he finished fourth in AL Rookie of the Year balloting.

Through his first 11 starts of 2012, Nova had been, in many ways, lucky again. Once again the run support was there, with New York putting up 7.4 runs a when Nova pitched, marking the 25th-best run support for any starter this year. The Yankees’ bullpen, typically a solid crew, had been virtually unhittable behind Nova, posting a 0.64 ERA in games he started. The Yankees’ defense had committed exactly zero errors during Nova starts. Those factors helped explain how Nova jumped out to a 7-2 record in 2012, and he’d extended his road winning streak to 10 games.

Five days after Keri wrote his column, Nova allowed one run in 7 2/3 innings against the Washington Nationals to improve to 9-2, 25-6 since the start of 2011. Since then, the mercurial righty is 1-4 with a 6.30 ERA in 10 starts. If you only include his last five starts, the numbers get much worse: 0-3, 8.36 ERA, with a hideous 1.82 WHIP.

The peripheral stats that pegged Nova as overrated in 2011 now point to an even more insidious conclusion: right now, Nova is a ground ball pitcher who is getting KILLED by fly balls. According to FanGraphs, Nova’s ground ball percentage has slipped from 52.7% in 2011 to 46.4% this year, not a good trend for a pitcher whose biggest weaknesses is leaving fat pitches up in the zone. And the numbers bear that out — Nova’s home run rate has more than doubled this season, all the way up to 1.50 homers per nine innings from 0.71 in 2011. That’s primarily because Nova’s HR/FB (the percentage of fly balls allowed that are home runs) has skyrocketed to 16.2% this season, a catastrophic figure for a pitcher like Nova, who relies on the consistent downward movement of his pitches. Last year his HR/FB number was 8.4%; in his truncated first season in the bigs in 2010, it was 9.5%. Nova has also shown a troubling lack of out-of-the-zone command when he’s ahead in the count (in other words, he can’t seem to waste a pitch on 0-2 or 1-2 like he should). Last night against Miguel Cabrera, both of Nova’s systemic flaws occurred at the same time on his way to the loss in a 7-2 Detroit Tigers victory.

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All of which brings me to the $64,000 — hell, $64 million, it’s the Yankees — question: Should Nova be dropped from the rotation when Andy Pettitte comes back at the end of August? I’ve already argued that Nova has slipped out of any potential playoff rotation, behind C.C., Hiroki Kuroda, Pettitte and Phil Hughes. Right now, though, Nova is pitching decidedly worse than Freddy Garcia, who is a passable 3-3, 3.95 ERA / 1.39 WHIP in seven starts since Pettitte broke his leg in late June. There’s no doubt that Nova at his best is superior to the ancient Garcia at his best. But Nova is so far from his best right now that it’s reasonable to wonder if he can get it back just by pitching through his slump.

Pettitte is due to come off the DL at the end of the August, though a mid-September return to the Yanks is more likely. Until then, Nova will pitch every fifth day unless his ERA for August is still north of 10.00 in a couple starts. But if the young righty can’t regain the sink on his sinking fastball or continues to mentally exit the game for innings at a time, a demotion to the minors or the bullpen should follow when Pettitte does come back. The Yankees have too many talented thoroughbred starters in the minor leagues to continue riding a lame horse.