Markakis was hit by a Chris Sale fastball with two outs and left the game, but he returned to the bench and watched the final out.
"It was more of a pinch than it was a direct blow, so we got lucky there," Showalter said.
Markakis apparently banged his right knee on a sprinkler head while diving for a ball, which could present more of an issue than Sale's 94 mph fastball.
"He brought it up to me," Showalter said. "You know Nicky, anytime he brings something up ... We'll see where we are tomorrow.
"I think we dodged a bullet with the hit by pitch."
Down on the farm, Dan Klein (UCLA) threw two scoreless innings in his debut with Double-A Bowie. He allowed two hits.