McLouth led off the top of the ninth inning when Kyle Drabek hit him with a 94-mph fastball on the outside of his right knee. Buck Showalter immediately lifted McLouth in favor of Chris Dickerson after McLouth "walked gingerly" down the first base line, according to Brittany Ghiroli of MLB.com.
The outfielder has been a solid contributor for Baltimore this season, entering Sunday batting .266/.336/.407. McLouth has also provided value with his defense and baserunning, as FanGraphs credits him with 2.4 WAR.
McLouth has been the team's primary leadoff man and left fielder. Michael Morse and Dickerson will likely split time in left if McLouth is sidelined for a few games, with Nick Markakis or Brian Roberts switching to the leadoff spot.
The Orioles defeated the Blue Jays, 3-1, helping the team keep pace in a tight AL Wild Card race.