For the second day in a row, Anthony Rizzo put the Cubs on his back.
Only this time, the result wasn't a win for his team.
The National League MVP frontrunner tied the game in the ninth inning, lifting a two-strike single into left field to score Dexter Fowler.
But Cubs reliever Mike Montgomery couldn't hold on, letting the winning run strut in on a walk-off single from Tyler Saladino in a 5-4 White Sox victory in front of 39,510 fans at U.S. Cellular Field Monday night.
Montgomery — acquired last week from the Seattle Mariners — has now given up two runs and recorded just two outs in a Cubs uniform.
He admitted he needs to be smarter in that situation in the ninth inning and also assured Chicago reporters his confidence isn't faltering despite a bad start with a new club.
"No, I felt really good today," Montgomery said. "I think it's really just a couple of pitches that I was trying to go up in the zone and just being a little bit smarter about. You gotta have a short memory in here.
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"It's obviously frustrating. It's the last thing I want to do — come here and not do well right away. I'm not gonna lose any confidence, though. I'm gonna go out there and trust my stuff and just kinda learn from it and move on and be ready for tomorrow."
The Cubs trailed all game as the White Sox touched up Jake Arrieta for a run in the third and then Todd Frazier drilled a three-run shot into center field with two outs in the sixth.
"It's obvious I just need to execute better there," Arrieta said. "I threw him a first-pitch cutter and he threw the bat in the stands, I think. Just needed to be more expanded with that pitch; it was middle-middle.
"He's in a situation where he's expecting balls in the strike zone. You gotta tip your cap. He put a good swing on it. Just really came down to that pitch and not being able to execute the way I needed to."
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After Frazier's homer, Javy Baez immediately responded and cut the Sox lead in half with a two-run shot in the top of the seventh following Miguel Montero's double.
Baez later started the rally in the ninth with a double down the right field line before promptly stealing third and then scoring on Dexter Fowler's single off Jose Abreu's glove.
Fowler advanced to third on Kris Bryant's single, but Bryant was thrown out trying to stretch his hit into a double, setting the stage for Rizzo's temporary heroics.
In the bottom of the ninth, Montgomery allowed a leadoff single to J.B. Shuck, who moved to second on a sacrifice bunt. Saladino then came through with a single up the middle, which Matt Szczur bobbled, ensuring there was no play at the plate.
Arrieta finished with four runs allowed on five hits and a pair of walks in six innings, following up his strong outing against the New York Mets last week with another up-and-down start.
But Cubs manager Joe Maddon really saw just one bad pitch from Arrieta.
"He pitched really well," Maddon said. "Six innings and gave up very few hits. Very light contact. And he gave up one home run.
"At the end of the day, man, we lost the game, but you cannot start denigrating people for one pitch or the fact that somebody didn't get a hit at the end. We played really well and they just beat us today on a home run and they made some defensive plays.
"I really think it's important always to truly evaluate what you saw and not just because you lose, denigrate people because of that. We actually played really well today and [Arrieta] pitched well."