Blue Jays manager John Schneider said Sunday that Heineman has been contending with back spasms lately, Keegan Matheson of MLB.com reports.
The back issue explains why Heineman will be held out of the lineup for a third straight game Sunday against the Twins, paving the way for Brandon Valenzuela to make another start behind the dish. While Alejandro Kirk (thumb) is facing a long-term absence, Heineman should split time with Valenzuela more evenly once he's 100 percent.