Rizzo hit a grand slam, Contreras launched two long solo homers and the Cubs kept pace in the NL wild-card race with a 17-8 win over the Pittsburgh Pirates on Friday.
Rookie Nico Hoerner hit a two-run shot for his first major league homer and had four RBI for the Cubs, who moved one game ahead of Milwaukee for the second wild card. The Brewers lost to the NL Central-leading Cardinals on Friday night.
Contreras, Hoerner and Nicholas Castellanos each homered in the first with the wind blowing out as Chicago scored five times -- and then kept on rolling -- after Pittsburgh jumped on Jon Lester for a 4-0 lead.
"Weirdly, I was expecting that response," manager Joe Maddon said. "I really thought that under the circumstances the energy level was great, then to answer as quickly as we did. I want to believe that's going to continue."
Contreras, who said he was just trying to hit pitches to right center, boosted his homer total to 23. The All-Star catcher has four home runs in six games since returning from a hamstring injury.
"I knew that we were going to have a good game," Contreras said. "We were hungry. It was just the first inning and we never gave up and we came back."
Hoerner elevated a low pitch to the center field batter's eye in his first plate appearance at Wrigley Field. He drove in two more runs with a single in Chicago's seven-run fifth.
The 22-year-old infielder made his debut with the Cubs on Monday at San Diego after the team announced All-Star shortstop Javier Baez would miss the rest of the season with a hairline fracture in his left thumb. Hoerner, who played at Double-A before joining Chicago, is hitting .350 with eight RBI through his first five games.
"To come here and contribute like he's been doing, hopefully that continues for us," Lester said. "He's been a little bit of a spark plug."
Castellanos' 26th homer, a two-run shot, tied his career high and was his 15th in 40 games with Chicago since arriving at the trade deadline from Detroit. He added his 50th double to tie for the major league lead.
Pablo Reyes had a double and triple among three hits, and two RBI. Kevin Newman had three hits and an RBI for Pittsburgh.
Lester (13-10) got the win despite allowing seven runs (four earned) on 11 hits in five innings. Alec Mills pitched the final three innings for his first save.
Pirates starter Steven Brault (4-5) was tagged for 10 runs on Chicago's five homers in 2 2/3 innings.
"Every mistake I made was a home run," Brault said. "It was just their day. It was a bummer, obviously."
The Cubs returned from a 3-5 trip to open their final regular-season homestand. Following a weekend series with Pittsburgh, Cincinnati comes to Wrigley Field for three games before St. Louis visits for the final four.
Contreras homered leading off the third. After the Cubs loaded the bases against Brault, Rizzo lined a 2-1 pitch to right for his fifth career slam and a 10-4 Chicago lead.
The Pirates scored three unearned runs in the fifth. The Cubs pulled away with seven runs in the bottom of the inning when nine batters in a row reached after two were out. Jason Heyward's pinch-hit double drove in three runs.
FRUSTRATED AND UPTIGHT
Cubs president of baseball operations Theo Epstein called his team's performance on its recent trip "uninspired" and "unacceptable" in radio appearance on Thursday. Before Friday's game, Epstein softened his tone and emphasized that no one was "being put on notice."
"I think everyone around the team is frustrated because we're not doing what we need to do," Epstein said. "I think we all feel this is a team that should be winning."
Before the game, Maddon said his team was playing "tight," despite a roster loaded with players who have winning postseason experience.
"When you play uptight, it's very difficult," Maddon said. "Our guys care too much, that's my interpretation. I want us to loosen up and play baseball."
Pirates: 1B Josh Bell left in the fifth with a groin injury and is day-to-day. ... CF Starling Marte was out of the lineup for a fifth straight game with a left wrist sprain he suffered while making a sliding catch on Sunday against St. Louis. ... The Pirates claimed LHP Williams Jerez off waivers from San Francisco and placed RHP Kyle Crick on the 60-day injured list. Crick needed surgery on his right index finger after a clubhouse fight with fellow reliever Felipe Vazquez.
Cubs: RHP Craig Kimbrel, on the IL with right elbow inflammation, threw a 24-pitch bullpen session on Thursday. Epstein said Kimbrel would toss another session on Sunday, but said there's no timetable for his return.
Pirates RHP James Marvel (0-1, 3.60 ERA) makes his second major league start when he faces RHP Kyle Hendricks (10-9, 3.33) on Saturday. Marvel allowed two runs in five innings in his debut against St. Louis last Sunday. Hendricks is 2-0 with a 2.67 ERA in his last five starts.
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Contreras belts 460 and 455 foot homers
Willson Contreras crushes a solo home run to center field in the first inning, then rips another one to center in the third to give the Cubs a 6-4 lead.