CHICAGO -- Long before he inserted Javier Báez into a pinch-hitting spot in the ninth inning against the Phillies on Tuesday night, Cubs manager Joe Maddon wasn’t even certain his star shortstop was available.

Earlier in the day, Baez had undergone an MRI on his bruised right ankle, which kept him from starting for the second straight night. But with the game tied in the ninth and the bases loaded, Maddon knew who he wanted -- if he could go.

Baez delivered his second career walk-off hit with a one-out RBI single that capped a 3-2 comeback win at Wrigley Field for Chicago's fifth walk-off victory of the season.

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It wasn’t until the ninth inning that Maddon was told trainers were taping Baez’s ankle to allow him to hit if needed.

“I said, ‘Why not?'” recalled Maddon, who admitted not knowing how the situation would play out when he sent Baez to the plate. “I just went with it.”

Baez came through after the Cubs loaded the bases, trailing 2-1. Kris Bryant led off the inning with a walk before Anthony Rizzo doubled. After Willson Contreras flied out and Phils reliever Juan Nicasio intentionally walked Jason Heyward, Bryant beat out a throw to the plate on Albert Almora Jr.'s fielder’s choice back to Nicasio to knot the game at 2. That brought up Baez, who hit for Daniel Descalso (0-for-4 on the night).

Baez drove a first-pitch slider from Nicasio into right field to take on the unlikely role of hero.

“I don’t even know what’s going on with him,” Bryant said. “It was awesome. He just goes up there and swings the bat -- it’s like if he didn’t have to run to first base, he wouldn’t. It’s like [he says], ‘I’m so good, I’m just going to get this hit and we’re going to go home.'”

Baez, who sustained the injury on Sunday night against the Nationals, was not available for comment after Tuesday’s game. Before the game, Maddon said Baez was still experiencing soreness in the ankle. Tuesday’s MRI did not reveal anything beyond the bruise.

The Cubs rallied after starter José Quintana threw six shutout innings while allowing just two hits and striking out four. But Brandon Kintzler gave up a two-out, two-run single to Andrew McCutchen in the seventh. Kintzler inherited the two runners from Carl Edwards Jr., who took over for Quintana with Chicago clinging to a 1-0 lead.

Quintana protected a 1-0 lead after Contreras’ RBI groundout scored Bryant from second base in the first inning. With one out, Bryant had singled and Rizzo walked. Contreras followed with a sharp grounder to short with both Bryant and Rizzo running.

And like he did in the first, Bryant’s aggressive baserunning factored into the ninth-run rally.

“I just give it 100 percent every time and try not to do anything stupid out there,” Bryant said. “It ended up working twice for me today.”

The Cubs appeared to add to their lead in the fourth inning when Bryant lined a double into the left-field corner. Kyle Schwarber, who had walked with two outs, scored from first before Phillies manager Gabe Kapler challenged that Bryant’s double had actually bounced out of play for a ground-rule double. Video replay overturned the original call, which sent Schwarber back to third base. With runners on second and third, Zach Eflin got Rizzo to fly out to keep Chicago's lead at only one run.

Despite that, the Cubs were able to rally when they needed. Although Maddon said he did not know what he would have done with Baez had Chicago not taken the lead, Baez made the decision a non-factor and didn’t waste any time doing it.

“He’s not going to wait around,” Maddon said of Baez. “He hadn’t played in a couple days, but he didn’t miss it -- he shot it down the right-field line. It was fitting.”