Jayson Werth Alex Brandon/AP

Jayson Werth left in ninth inning of Saturday’s 10-9 loss to the St. Louis Cardinals with cramping in his hamstring. Nationals Manager Davey Johnson pulled Werth to start the inning, moved Bryce Harper to right field and Eury Perez made his major league debut by taking over center field. Werth said the cramping wasn’t expected to be a serious issue.

Werth has been the Nationals hottest hitter and an on-base machine since his return from a broken wrist on Aug. 2. He is hitting .350 (35 for 100) and scoring 20 runs over the past 27 games. He started in right field and smacked a double and scored a run in Saturday’s game.

To be cautious, Johnson took Werth out. The hot and humid weather, and a near three and a half hour game, likely didn’t help.

“It’s been four, five years since I cramped up during a game,” Werth said. “Hopefully it’s just that, and no big deal.”

Werth didn’t start on Aug. 7 because of leg tightness as he was working back into game shape from his long stint on the disabled list with a broken wrist. He also missed a game on Aug. 13 with a sore ankle. Perez, 22, was called up on Saturday, the first day of roster expansion and played one inning and made an inning-ending catch deep in left field.