Biddle, Philadelphia's top-ranked left-handed prospect, was hit by a liner after throwing his second pitch to Daytona leadoff man Rubi Silva. He managed to get the ball to first baseman Jim Murphy for the out, but was pulled as a precautionary measure by manager Chris Truby.
"He's fine," Truby said. "He's just got a bruise, I believe, on his left forearm."
Truby was unsure whether Biddle had an X-ray, but he had undergone other tests. The skipper added that, as of late Tuesday, Biddle was expected to make his next start in the rotation.
Garett Claypool replaced Biddle on the mound, working the next 3 2/3 innings as the Threshers went on to beat Daytona, 7-3.
Biddle, the Phillies' first round pick in 2010, was coming off his best start of the season on April 26, when he held the Cubs to one earned run over six innings in a no-decision. He'd been charged with 15 runs over his first three starts to begin the year, his first in the Florida State League.
The Philadelphia native went 7-8 with a 2.98 ERA in 25 outings last season at Class A Lakewood, striking out 124 batters in 133 innings.