The Nationals placed right fielder Bryce Harper on the 10-day disabled list with a "significant bone bruise" in his left knee, the team announced Sunday.
Martin left the game Friday night after the first inning when he grounded out.
Danny Barnes, Leonel Campos, Ryan Tepera and J.P. Howell combined to pitch three scoreless innings in relief.
Happ, who was dominant in his previous two outings, allowing only two runs combined, struggled in the first inning against the Pirates. Manager John Gibbons also earned his 700th career win as Blue Jays manager. He left after Toronto put runners at second and third with no outs in the seventh. He improved to 3-0 in his last three starts.
In five games with the Blue Jays this year, Ohlman is 2-for-9 (.222) with an RBI.
Juan Nicasio pitched around a single in the eighth for Pittsburgh (58-58).
Toronto took a 5-1 lead later in the first on a double steal by Kevin Pillar and Goins, which saw the Blue Jays shortstop plate.