It would be incorrect to call it a "huge" win for the Pirates, because that implies a measurable quantity. Until Andrew McCutchen tied it with a hard-hit eighth-inning homer and Walker won it with a much softer blow, the Bucs were staring at losing a third consecutive game they had led into the eighth inning.
Under those conditions, they had been 74-4 in 2013. So, a major lifeline?
"It's important. Big," manager Clint Hurdle allowed. "Winning jacks you up. Losing gives you perspective. We had enough perspective the last 48 hours."
Acquired from the New York Mets in a Friday deal for power, Davis' first three hits for Pittsburgh had all been opposite-field liners into left.
However, with the bases loaded and none out in the fourth inning, Cincinnati right-hander Mike Leake's first pitch to him was a 90-mph fastball Davis could pull -- and pull it he did, into those inviting seats in the right-field pavilion, even with a bat that cracked on contact.
"It felt good," Davis said of the connection. "If anything, I felt it might be caught at the wall. I didn't know -- I hadn't played here enough to really know the stadium well enough where I could just put my head down and start jogging."
It was the biggest blow of the game, but not the decisive one. That was delivered by Walker in the final frame off J.J. Hoover after the Bucs mounted their threat on consecutive walks with one away by Russell Martin and McCutchen.
Walker looped his single over second baseman Brandon Phillips to right fielder Jay Bruce, whose throw home appeared to be on time. But the ball squirted through catcher Devin Mesoraco as Martin slid in.
The soft hit was sweet vindication for Walker, who consistently hits into more hard outs than anyone else on the team.
"Yeah, definitely," he said, flashing a smile. "Any time you can not hit it on the barrel and find some grass to score a run, especially to win a game, is good. Pretty good retribution for some balls that were hit hard and were caught."
The victory went to right-hander Jared Hughes, who worked out of a jam to blank Cincinnati in the ninth in his first appearance following his pregame recall from Triple-A Indianapolis.
Davis' blow had endowed Francisco Liriano with a 4-2 lead that could not survive two late Reds rallies, including a two-spot in the eighth that put the Bucs in a 5-4 hole.
McCutchen then drew the Pirates even with a solo homer to begin the eighth, his third hit of the game coming off lefty reliever Manny Parra.
Davis' third career grand slam was his second this season, both against the Reds. As a pinch-hitter on April 5, he had connected off Hoover to give the Mets a 6-3 walk-off in Citi Field. Consider that his farewell shot to New York.
This was his hello shoutout to Pittsburgh.
"We did have that conversation [on the bench]," Hurdle insisted. "We said, 'Two in one month against the same team would be kind of cool.' But I don't think we had him breaking his bat on the swing."
This is where it gets just a little weird. The only others in Major League history to hit two grand slams against the same team for two different teams in the same season were Mike Piazza and Ray Boone -- whose nickname was "Ike," and whose grandson, Aaron, was in ESPN's booth Monday night calling the game.
Liriano still had a 4-3 lead when the Reds began the eighth with singles by Phillips and Todd Frazier that put runners at the corners for Bruce, who greeted another lefty, reliever Justin Wilson, with a tying RBI double into the left-field corner.
The score didn't remain tied for long. After an intentional walk of Ryan Ludwick, the scalding Mesoraco singled to deliver Frazier, although left fielder Marte's throw cut down Bruce at the plate and there was no more damage.
The Reds jumped into a quick 1-0 lead in the first. With Billy Hamilton running from third, Pedro Alvarez fielded Phillips' one-out grounder and threw cleanly to Martin behind the plate, who had the ball squirt out of his mitt as the runner slid in. That made it a wholly gift run, because Hamilton had been hit by Liriano's first pitch of the game, then motored all the way to third on Joey Votto's bouncer slightly to the right of the mound.
The Reds were a bit more expedient to double their lead in the third, Phillips and Frazier drilling consecutive doubles with one away.
So, having given up more runs (two) than in eight of his 11 PNC Park starts last season, Liriano was again looking quite ordinary. He stepped out of that mode in the middle innings -- blanking the Reds on one hit the fourth through the sixth.
"Shutdown innings is what everybody talks about," Hurdle said. "Frankie is our go-to guy. He leads the staff with experience and with the way he works. He knew where our bullpen was tonight (spent, after Sunday's 14-inning match with the Brewers)."
Liriano was back to staggering in the seventh. Hamilton's sacrifice fly cut his lead to 4-3, bringing him to the edge he went over the next inning. Five starts into the season, the lefty remained winless and his ERA climbed to 4.22.