CHICAGO -- Jon Lester described the conditions at Wrigley Field on Friday afternoon as miserable. Cubs manager Joe Maddon chuckled and quipped that everyone on the diamond or in the dugouts was melting. Florida native Anthony Rizzo smirked and had no complaints.

"I like the heat," Rizzo said after the Cubs' 6-5 win over the Padres.

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Rizzo certainly backed up that talk in the third inning, when he lifted a center-cut fastball from San Diego lefty Eric Lauer and sent it towering over left field and into the first row of the bleacher seats for a grand slam. That was one of two homers that the Cubs launched in support of a gutty six-inning performance from Lester in Chicago's sixth win in seven games since the All-Star break.

Given the warts that still existed within the win, the National League Central-leading Cubs will take it. Maddon said he would not overanalyze some of the sloppy plays in the field due to the heat index sitting at 106 degrees at first pitch. The issue that Maddon did address -- both before the win and again during his postgame press conference -- was Chicago's persistent struggles against lefty pitching.

"We've been terrible. We have to be better," Maddon said before the game. "If you look at the overarching, overall numbers, they're not good, and we have to be better at that. And we have guys that are really good against lefties that haven't shown that yet."

On the surface, Friday's victory was a step in the right direction. The Cubs scored five runs against Lauer and chased the left-hander from the game after 4 2/3 innings. Rizzo launched the slam in the third -- the fourth four-bagger of his career -- and Javier Báez belted a solo shot off Lauer in the fifth.

And, as Lester pointed out, a win is a win is a win.

"At the end of the day, a win goes right there in that 'W' column," Lester said, "and we all move on to the next one. I'll take them any way we can get 'em."

Prior to Friday's win, however, Maddon cited Albert Almora Jr., David Bote and Addison Russell as three players that the Cubs need to get back on track against southpaws down the stretch. The trio was in the starting lineup against Lauer and went a combined 1-for-7 with five strikeouts. The lone hit was an infield single by Almora out of the leadoff spot. Russell (batting fifth) and Bote (seventh) each struck out twice.

Entering Friday, the Cubs ranked 15th in the NL with a .234 average against lefties, while ranking 11th in wOBA (.319), OPS (.752) and wRC+ (94). Almora had a 48 wRC+ against left-handers this year, compared to a 101 mark in 2018. Russell (88 wRC+ in '19 after 102 in '18) and Bote (42 wRC+ in '19 after 134 in '18) have both declined in that department, too.

Dating back to June 1, Rizzo (72 wRC+), Almora (53), Baez (51), Bote (13), Kyle Schwarber (minus-three) and Jason Heyward (minus-44) were all below MLB average against southpaws, entering Friday.

"I'm still saying there's another level of us that I want to see," Maddon said. "We've got to hit lefties, man. We've got to figure that part of it out. That's a big part moving down the road. And we have guys in our lineup that historically have done that that aren't doing it right now."

Rizzo was asked if he knew what was behind the team's struggles against left-handers this season.

"I really don't know," Rizzo said. "It'll be nice -- we get another lefty tomorrow [San Diego's Joey Lucchesi]. I'm sure we'll face a lefty or two in San Francisco [next week]. We don't see them a lot regularly, so when we do, it's good to get your at-bats off them."

And the Cubs did manage enough success against Lauer to set up some game-changing swings.

In the third, that two-out infield hit from Almora came ahead of a single from Baez. Kris Bryant, who has a 252 wRC+ against lefties dating back to June 1, then slipped into a 1-2 count against Lauer before working a walk to load the bases. That sequence made Rizzo's blast to the bleachers possible.

Maddon called Bryant's walk "possibly the biggest at-bat of today."

There were just enough of those moments for the Cubs to make the most of a miserably hot day.

"You could sit there and we could be negative about things," Maddon said. "But it was extraordinarily different for both sides. We did win the game. I don't want to overlook that."