Two outs later, Starling Marte flashed his second homer of the year over the left-center-field fence, turning another bummer into a 6-5 victory.
"Oh, very exciting. It felt great," said Marte, who at the end of his tour of the bases following his first career walk-off hit was welcomed at home by … what else, a mob flashing smiles.
Those smiles began forming the instant Alvarez connected with Santos' 1-0 pitch.
"Everyone knows how strong, how good he can be, when he puts the barrel on the ball like that," said Walker, who recognized that sound. "I knew it was gone as soon as he hit it. I know that sound off his bat -- and the look on his face."
Five pitches later, it was Marte's turn to drop Santos' chin just a little lower with his third blown save.
"It just seems like everything I throw they hit and they barrel up. It's just frustrating as heck," Santos said.
Maybe the Bucs were just upset that Santos would take the PNC Park mound wearing uniform No. 21 -- a sacred numeral in these parts.
"What a really good team victory," said manager Clint Hurdle, who actually had a very big hand in it.
Marte's heroics -- the game-winner was his fourth hit of the night -- came from the No. 6 spot in the batting order, just more evidence of the work of the Pirates' mad scientist.
In the three games since he was dropped out of the top of the batting order, Marte is 7-for-12. As a struggling leadoff batter, he had seven hits in his previous 41 at-bats.
"I'm never surprised by what people do when you give them a chance to show what they can do. Just changed his scenery a little," Hurdle said.
So the manager passed on that laurel. Then, how about the constant lineup juggling that finally produced a good combination Friday night, placing two hot hitters back-to-back in the lineup. Walker returned to the two-hole ahead of Andrew McCutchen and the pair went 6-for-9, with three runs and two RBIs.
"That's all we've been missing - some consistency," said McCutchen, who raised his average to .309 with his thee hits. "Hopefully, this momentum can propel us."
Hurdle expressed the same hope. The manager, however, realized it is a hope already often expressed this season, but not yet answered.
"This is about our fifth opportunity for a spark," he said. "We'll see what this does."
For starters, it kept the Pirates out of the National League Central cellar which, given the Cubs' afternoon victory over the Cardinals, seemed to be their destiny until the awakening.
The Pirates thus survived an off night by starter Gerrit Cole to snap their latest losing streak at three games.
Playing a major role in the comeback win was Casey Sadler, who made his big league debut to complete the uphill climb from having been a 25th-round pick in the 2010 First-Year Player Draft. Sadler put up zeros in the seventh and eighth innings.
"Surreal, I guess, is the word for it. It's something I've dreamt of for a very long time, and not a lot of people get to feel that," said the 23-year-old Oklahoman. "My heart was racing so much, I honestly felt like it stopped a little bit. But it's still a game; they still have to try to make good contact if I make my pitch."
Mark Melancon then worked the ninth to earn the relief win.
Toronto leveled the first blow, converting a two-out rally in the first that could've been bad news for a Pirates team struggling offensively. Jose Bautista and Edwin Encarnacion doubled back-to-back for the 1-0 lead.
Jordy Mercer had a solid opportunity for a third RBI in his 70th at-bat, coming up with the bases loaded and none out in the second, but it wasn't to be. He got in a run, but only by grounding into a double play, which tied the game at 1, but aborted a more productive rally.
Walker doubled with one away in the third and came in on McCutchen's single for a 2-1 lead. When Alvarez followed with another single, the Pirates were set up for another run at a bigger inning. This, too, ended with a double play, on a hot smash to third by Gaby Sanchez.
That one-run lead couldn't survive Juan Francisco's double and Brett Lawrie's sixth homer a few minutes later in the fourth. Toronto added to its lead in the fifth, Bautista doubling to score Jose Reyes, who had singled and stolen second.
The volume of high-pressure pitches each starter needed to make to keep their team in the game took its toll on both starting pitchers, and they were gone after five.
Cole's outing matched his briefest in 15 career starts at PNC Park. He allowed seven hits and four runs, all earned, while walking one and striking out six.
Brandon Morrow was not at his best, but somehow got the better of Cole, spreading 11 hits -- if that's possible in five innings. He was charged with three runs and walked one -- seven fewer than in his last outing -- and fanned two.
In the sixth, Steve Tolleson's pinch-hit RBI triple off lefty reliever Justin Wilson made it 5-2.
The Bucs got within striking distance in the fifth, scoring with that familiar combination: Walker doubled and came home on McCutchen's single.
A little later, just as some people may have imagined hearing "Taps," was that "Reveille?"
"Every season, every battle, will have a low point, and that last road trip was about as bad as it can get," Walker said. "There was a lot going on, no fun. But the farthest thing from our mind is pressing in May."