The Yankees have used a conveyor belt of pitchers this season. Luis Severino was No. 30, a total that leads the AL and is the second-most for a season in franchise history, after last year’s 33.

Beyond the natural attrition of a season, the purpose of this rapid turnover has been to keep the back of the bullpen stocked with fresh arms to make sure Joe Girardi always had an alternative (or two) to call upon if there were an injury or extra innings or a short start. The Yankees have recalled 32 players this season (tied with the Dodgers for MLB’s most) and optioned 37 (second in MLB to the Dodgers’ 44).

By having relievers with options, the Yankees effectively have had more than a 25-man roster this season. It is why, for example, they have used 14 rookie pitchers, which ties their franchise record from 2007 (where have you gone, Colter Bean and Matt DeSalvo?).

But, in a way, this also has been an audition. Because it sure sounds like one way the Yankees are going to attack the final month – in many ways to try to cover for an underwhelming rotation – is to flood the game with relievers, if necessary.

If Joe Girardi literally has to go inning by inning with a new guy, so be it.

So get ready for a lot of Girardi walks to the mound and lots of excruciatingly long games.

“I would think so,” Yankees general manager Brian Cashman said of bringing up a bevy of relievers on Sept. 1. “Obviously, we have to get through August, but in September you can bring everyone you want to bring.”

Forgive an aside here to continue my long-standing rant about the folly of expanded rosters in September. How ridiculous is it to allow games to be played one way for five months and then, in the most precious regular-season month of all, have teams able to basically eliminate matchup strategies because rosters have extra relief specialists and/or pinch-hitters? How ludicrous is it that opposing teams carry different numbers of players? In its most extreme form, one team can have 40 players facing a team with 25. What would we think if one NFL team could dress 55 players and the other 45?

But until MLB officials come to their senses, these are the rules. And, just like using the option system to create a roster larger than 25, the Yankees can legally exploit this, too.

In the best scenario, the Yankees would have Masahiro Tanaka healthy, Ivan Nova fully in his groove after Tommy John surgery, the strong recent version of Nate Eovaldi, a returned Michael Pineda, a revived CC Sabathia and a revelatory Luis Severino — and their bullpen acting like a standard bullpen.

But the first 65 percent of the season has suggested that isn’t happening. For all the talk about the second-place Blue Jays’ problematic rotation, the Yankees starter ERA (4.35) was worse than the Blue Jays’ (4.22) – and Toronto just added David Price. It is the fourth-worst rotation ERA in the AL, and the Yanks are averaging a shade more than 5 2/3 innings per start, sixth-worst in the AL.

Already we have seen Girardi’s itchy finger. So if relievers have to be on red alert even earlier for Sabathia in September, so be it. In theory, Pineda could come off the DL in September and build his innings back up in the majors because he will have the pen support with relievers such as Adam Warren and Bryan Mitchell capable of giving some length.

Beyond the familiar quintet of Andrew Miller, Dellin Betances, Justin Wilson, Chasen Shreve and Warren, the Yankees will probably turn to Mitchell, Braden Pinder, Nick Rumbelow and Jacob Lindgren, who the Yanks think will be viable in September after elbow surgery to remove bone spurs. Caleb Cotham and Nick Goody – two guys who pushed from off the radar to the majors – are considerations, and others might be, as well.

The Yankees already are averaging 10 outs a game from their pen – among the most in the majors. Just wait until September.

Yankees line up righties vs. lefty-slaying Jays

With Pineda on the DL and Severino just having made his debut, the Yankees have their best three starters lined up to face the Blue Jays: Nathan Eovaldi, Ivan Nova and Masahiro Tanaka. Because if you are facing Toronto right now, you better have a righty starter with high-end stuff.

Toronto’s lineup already was terrific even before acquiring Troy Tulowitzki. His addition, however, made the Jays even fiercer and more lethal against lefties as he joined righty mashers Josh Donaldson, Russell Martin, Jose Bautista, Edwin Encarnacion and Chris Colabello (Bautista and Encarnacion actually have done better vs. righties this year).

In Tulowitzki’s first eight games following the trade, Toronto was hitting .344 vs. southpaws with an 1.106 OPS. For the season, the Blue Jays have an .841 OPS vs. lefties. That is the best in the majors since the Yankees had an .846 OPS against lefties in 2009, when they opened their new launching-pad Stadium. In 2015, the Blue Jays lead the second-place Yankees (.783) by 58 points, roughly the same distance between the Yankees and the eighth-best Astros (.726).