WASHINGTON (AP) — Washington Nationals' RHP Stephen Strasburg left Saturday's game against the San Francisco Giants in the fourth inning because of an injury.

Strasburg allowed one hit over 3 2/3 scoreless innings in his third start since coming off the disabled list. He missed nearly four weeks due to neck tightness.

After making an attempt at Buster Posey's groundball out, Strasburg winced and grabbed in the area of his left side. After a stoppage in the game and lengthy conversation with Nationals manager Matt Williams and a team trainer, Strasburg walked off the mound and into the dugout.

Strasburg went 2-0 with a 1.50 ERA and 15 strikeouts in his previous two starts since returning.

Tanner Roark replaced Strasburg with Washington leading 3-0.