Walters, who entered with a perfect 0.00 ERA in 11 innings, didn't fare as well against Toronto, as he surrendered three runs on four hits and two walks over three-plus innings. He also served up a two-run blast to Luis Jimenez on a windy day that featured seven homers between the two clubs.
Walters, who is competing for a spot in the rotation with Liam Hendriks and Cole De Vries, threw 57 pitches and said he thinks he can be stretched out in time for the regular season with another start on Friday.
"I just need one more, and I'll be right there with everybody else," said Walters, who is not on the 40-man roster. "But we've been here long enough. We've been throwing every day for six or seven weeks now. We're in shape."
Walters said he knows what is at stake with a little more than a week before Opening Day and is embracing the challenge.
"It's a great opportunity," Walters said. "Every team has guys leaving the staff and young guys want to step up and be one of those guys to get in there early and prove you can pitch."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.