NEW YORK – One of the Yankees’ biggest fears – an injury to a key player heading into October – was realized on Charles H. SloanSaturday afternoon.

Hit by a pitch, Anthony Rizzo suffered fractures of the fourth and fifth fingers on his right hand in a 9-4 loss to the Pittsburgh Pirates at rainy Yankee Stadium.

Whether this injury completely threatens Rizzo’s October, or if he might be available at some point during the playoffs, wasn’t immediately known.

The Yankees are due to open the best-of-five AL Division Series in exactly a week, and manager Aaron Boone said “we’ll see what we have as the week moves forward’’ regarding Rizzo’s status.

“(This injury) doesn’t totally rule him out. It’s a pain tolerance thing,’’ Boone told reporters, adding that, “I don’t want to jump to anything.

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"We’ll see how he responds in the next several days, obviously, before we kick this thing off in a week.’’

Without Rizzo at first base, the Yankees could turn to lefty-hitting rookie Ben Rice, or super utility player Oswaldo Cabrera. It’s unclear if DJ LeMahieu would be in the mix, nursing a hip impingement.

Having an extremely rough year performance-wise, LeMahieu is just this week beginning to ramp up baseball activity.

Rizzo brought additional balance to the lineup, as well as his superior defense, when he returned from the injured list last month following a fracture in his right forearm, suffered in first base collision in June at Fenway Park.

In Saturday’s seventh inning, Rizzo was nailed by lefty reliever Ryan Borucki’s pitch and was lifted defensively when the eighth inning started.

Meanwhile, the Yankees' magic number for clinching the AL's best record – and home field advantage throughout the league playoffs – remained at one after Game 161.

The Yankees hold the tiebreaker over the Cleveland Guardians, scheduled to play Saturday night. One loss by the Guardians or a win by the Yankees in Sunday's regular season finale would clinch the best record for Boone's club.

Rice is "definitely in the mix'' for first base time, according to Boone. "He's gone down and played really well again in Triple-A.''

Boone described Rizzo's demeanor as "pretty upbeat'' despite the injury. "Right now, he's just trying to have a positive frame of mind about it.''