Kelvin Herrera hurt himself while running toward first base after fielding a ninth-inning grounder. (Wendell Cruz/USA Today Sports)

NEW YORK — Kelvin Herrera entered Manager Dave Martinez’s office at Citi Field on Sunday morning with a request: He wanted to pitch in Sunday’s game against the New York Mets, no matter the situation. Herrera, who had not pitched in five days, needed the work. So Martinez obliged, inserting the right-hander in the ninth inning with Washington leading 15-0. The plan, Martinez said later, was for Herrera to throw a maximum of 15 pitches. Koda Glover was warm and waiting.

Herrera didn’t reach that number. He dropped to the ground writhing in pain at nine pitches after fielding a groundball and running to first base to make a put out. He got the out but had to hop on his right leg for the final few paces. He couldn’t put any weight on his left leg, which was examined for a few minutes before a cart whisked him away.

After the game, a 15-0 victory for the Nationals, Martinez said Herrera didn’t suffer an Achilles’ injury, which was the initial fear. Instead, he injured the top of his left foot. X-rays on Sunday evening were negative, but he will undergo more tests Monday to see whether he has ligament damage, according to a person with knowledge of the situation.

“I don’t know anything,” Martinez said. “… He said it was the top of his left foot. That’s all I know.”

Herrera, who was on crutches after the game, hadn’t pitched since he logged an inning Tuesday, which was his only appearance since Aug. 7 because of a stint on the disabled list. A season-ending injury would be devastating for the impending free agent, whose stock has dropped since he joined the Nationals in mid-June. Before Washington acquired him, Herrera pitched to a 1.05 ERA in 27 games for the Kansas City Royals. In 18 2/3 innings with the Nationals, Herrera has posted a 4.34 ERA. He has been a significantly worse pitcher but has been asked to close with Sean Doolittle on the disabled list.

Ryan Madson is expected to rejoin Washington’s bullpen as early as Monday and is the obvious replacement for Herrera, both on the roster and in the closer role. But the Nationals could call up a second reliever to replace Jefry Rodriguez because Thursday’s off-day means they won’t need a fifth starter until rosters expand Sept. 1. Rodriguez tossed six scoreless innings Sunday and isn’t slated to pitch again until Saturday. The Nationals could decide to use that spot to bolster their bullpen or add a fifth player to their bench as they head into a three-game series against the Phillies in Philadelphia starting Monday.

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