MILWAUKEE -- With the temperature nearing 100 degrees with humidity levels hovering near 80 percent, the last thing anybody in either dugout wanted Sunday afternoon was a four-hour baseball game.

Of course, in retrospect, the Chicago Cubs probably aren't complaining too much.

Anthony Rizzo had a three-run double in in a five-run seventh inning as the Cubs rallied for a 6-5 victory over the Milwaukee Brewers at Miller Park.

"That was beyond hot out there today," Chicago manager Joe Maddon said. "Smoldering, sweltering, volcanic, however you want to describe it. I give our guys a lot of credit for hanging tough under those conditions."

Tommy La Stella had three hits and reached base in all four of his trips. Ben Zobrist finished with two hits and a walk and drove in a pair of runs.

Cubs starter Jon Lester struggled on a sweltering and humid day, allowing four runs on four hits and five walks while striking out seven in four-plus innings.

"I'm usually a lot cleaner than that," Lester said. "But I kind of minimized the damage there and just tried to move on, move on to the next inning and I was able to do that."

Milwaukee stole four bases against Lester, with three coming in the first inning as Jonathan Villar drew a leadoff walk, swiped second and third then scored on a sacrifice fly by Hernan Perez.

Ryan Braun singled, stole second and took third on an single by Jonathan Lucroy and then scored on Chris Carter's RBI single as Milwaukee took a 2-0 lead.

The Brewers added two more in the fourth to take a 4-0 lead but couldn't capitalize on big opportunities. Milwaukee left the bases loaded in two innings and stranded 12 runners on the day.

"They had opportunities to score a lot more but they didn't so I took some solace in that thought," Maddon said.

After being held scoreless through five innings by Junior Guerra, Zobrist put the Cubs on the board with a run-scoring single in the sixth.

Guerra got out of the inning without further damage but gave way after retiring Javier Baez to open the seventh and the Cubs finally broke through against left-hander Will Smith (1-3), who allowed two straight singles before La Stella's double made it a 4-2 game.

Smith fell behind 3-0 to Kris Bryant, resulting in an intentional walk that loaded the bases for Rizzo, who slapped a double to the gap in right-center to clear the bases and put the Cubs up 5-4.

Zobrist made it a 6-4 game with an RBI single but ended the inning trying to steal second.

The late rally spoiled a quality start from Guerra, who gave up five hits and walked four but allowed just one unearned run over 6 1/3 innings.

"It was a long game," Counsell said. "We had some opportunities to add on runs in general, just to score runs and we didn't capture those opportunities. We had a couple defensive mistakes that hurt us. You combine those two things, it kind of spoiled what was a great day by Junior Guerra again."

Joe Nathan (1-0) returned to the majors for the first time since April 6, 2015, and earned the victory by striking out the heart of Milwaukee's order in the sixth inning after allowing a leadoff triple and walk.

"I knew I was in a tough spot," said Nathan, who underwent Tommy John surgery last April. "I just tried to tell myself to stay within myself and make pitches. Almost tell myself, 'Listen, now let's take the results out of it, let's try to get some quality pitches and see what we can do.'"

Kirk Niewenhuis hit a solo home run in the ninth off Hector Rondon, who earned his 18th save of the season.

NOTES: Chicago activated RHP Joe Nathan from the disabled list. The 41-year-old hasn't pitched since April 6 of last season and underwent Tommy John Surgery later that month. He was signed by the Cubs in May. To make room for Nathan on the active roster, RHP Adam Warren was optioned to Triple-A Iowa. ... Cubs manager Joe Maddon gave OF Dexter Fowler a day off Sunday. Fowler is 3-for-8 with a double and a home run since returning from the disabled list Friday. Maddon said Fowler's right hamstring was sore but expected him to be back in the lineup Monday against the White Sox. ... Milwaukee OF Jake Elmore made his third start of the season, handling center field in place of Kirk Nieuwenhuis. It was Elmore's second career start in center. ... Brewers INF/OF Hernan Perez extended his hitting streak to eight games with a sixth-inning triple.