"His first outing. We're not worried about him," manager John Gibbons said soothingly of Sanchez, who suffered from his own and others' mistakes.
The Jays have 31 more exhibition games to get it right.
Kevin Pillar homered for Toronto, which made it close with two runs in the eighth and another in the ninth when the Jays had the bases loaded.
Pedro Alvarez, Jung Ho Kang and Elias Diaz homered for the Pirates, who led 6-0 early and outhit the Jays 14-11.
Gibbons preferred to see the positives in a predictably sloppy spring training opener that saw both teams empty their benches.
"We made a run at them ... we had a lot of opportunities but we couldn't really cash in," he said. "But the guys hung tough."
Dalton Pompey, competing for the Jays' open centre-fielder spot, engineered a run in the third when he singled, stole second, took third on a sacrifice fly and scored on a groundout.
With left field open for the time being due to Michael Saunders' knee injury, Gibbons switched Pompey to left and Pillar to centre in the fifth. Pompey responded with an acrobatic catch but then lost a fly ball that dropped in for a double and scored a run.
Reliever Wilton Lopez provided the Jays' only 1-2-3 inning, in the seventh. And six-foot-five beanpole Miguel Castro yielded only a single in an effective eighth inning.
"First time out there, he made it look easy," Gibbons said of the 20-year-old Castro. "I thought Lopez looked good too."
The three-hour 17-minute contest was the Jays' first under Major League Baseball's push to shorten games, with a clock in the outfield counting down time between innings.
"I didn't even notice it really," Gibbons said of the changes.
Sanchez finished last season as Toronto's closer but is being given the chance to earn a regular spot in the rotation.
Five runs (two earned) in 1 1/3 innings proved to be a tough start for Sanchez, who did not give up an earned run in six spring training games last year. He exited after 10 batters Tuesday.
"Just today wasn't my day," said the 22-year-old Sanchez, who was keeping his outing in perspective. "But I can learn from that."
It started well for the Jays with two fine fielding plays. First Sanchez stabbed a Jeff Decker liner aimed at his head. Then, off-balance after fielding the ball near home plate, Martin threw out Sean Rodriguez. A two-out error by third baseman Josh Donaldson left men on first and second, however, and Alvarez punished Sanchez with a three-run homer.
"It's spring training for everybody," said Sanchez. "You can't go out there and rely on guys making plays and (umpires) making calls, you've got to make your pitches and I didn't do that today."
A Decker double in the second drove in two more runs and ended Sanchez's afternoon on a sunny 25-degree day before 4,593 at Florida Auto Exchange Stadium.
Gibbons rolled out a strong lineup with shortstop Jose Reyes at leadoff, followed by catcher Russell Martin, right-fielder Jose Bautista, designated hitter Edwin Encarnacion, Donaldson, first baseman Justin Smoak, second baseman Maicer Izturis, Pillar and Pompey.
Pittsburgh starter Casey Sadler, who went 11-4 with a 3.03 earned-run average last season with Class-AAA Indianapolis before being called up, faced just six batters in his two innings with a Donaldson double play erasing a walk.
The Pirates went deep into the alphabet with their pitchers, showcasing Stolmy Pimentel, Arquimedes Caminero and Bobby LaFromboise among others.
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