CHICAGO -- If left-hander Travis Wood could pinpoint why he pitches so well at his home ballpark, Wrigley Field, he would bottle it up take it with him on the road.

Whether it is confidence or comfort that makes Wood so successful at Wrigley this season, the Chicago Cubs will gladly take his strong outings whenever he is on the mound. Wood limited the Milwaukee Brewers to two runs on two hits in seven innings on Sunday to lead the Cubs to a 4-2 win.

Welington Castillo and Mike Olt each homered to provide the offense Wood needed to improve to 3-1 with a 2.45 ERA in five home starts.

"We only get to do this once every five days so I guess it's kind of a lot of getting built up, ready to go and try to leave everything out on the field," Wood said of his success at Wrigley. "It's been working pretty well so far."

Milwaukee had the tying run at the plate in the ninth inning against right-hander Hector Rondon. Right fielder Ryan Braun doubled to center field to start the ninth, but Rondon didn't let Braun advance. Rondon struck out catcher Jonathan Lucroy, got first baseman Mark Reynolds to pop out and struck out left fielder Khris Davis to earn his fifth save in six chances.

The Cubs (15-27) had seven hits off Brewers starting pitcher Marco Estrada, all extra base hits, to help build a 4-0 lead. The win was only the Cubs' fourth in their last 14 games.

Estrada was not happy with start and said it was "plain and simple, terrible."

"It's just a bad-pitched game," Estrada said. "I didn't even give the guys a chance. Four runs isn't going to cut it. I've got to start throwing more strike ones and locating the off-speed pitches."

The Brewers (27-17) failed to capitalize on Wood's command issues to start the game. Wood (4-4) loaded the bases with three walks -- two coming with two outs -- but got out of the jam by getting Davis to hit into a fielder's choice on a nice defensive play by Olt at third base. Wood said he made a minor adjustment after the first inning to fix his issues.

"For the most part I was kind of flying open there in the first," Wood said. "We were able to make (an adjustment) and roll on from there."

Second baseman Rickie Weeks' two-run homer in the fifth gave Milwaukee its only runs of the game.

Wood (4-4) kept Milwaukee without a hit for the first 4 1/3 innings and finished the game having surrendered only two hits. Wood notched his fifth quality start of the season behind his seven-inning effort that included seven strikeouts and three walks on 103 pitches.

The Cubs' catcher, Castillo, homered on a 1-1 changeup off Estrada (3-2) left up in the zone for a 2-0 lead in the second.

Back-to-back two-out doubles from shortstop Starlin Castro and Castillo in the third extended the Cubs' lead to 3-0.

"He's scuffled with his location all game," Brewers manager Ron Roenicke said of Estrada. "His off-speed stuff, he wasn't throwing for strikes and if he was they were up in the zone. ... His command, his pitch count goes way up early, that's the second game in a row he's done that, so we'll get him back on track."

Olt hit his team-leading ninth home run of the season to lead off the fourth. Olt crushed a fastball Estrada left down the middle on a 2-0 pitch for a 4-0 Cubs lead. Estrada needed 99 pitches to last only five innings after giving up four runs on seven hits.

"I just wanted to be aggressive and get a good pitch I could hit," Olt said. "I was able to do some damage."

Milwaukee broke through in the fifth. Center fielder Logan Schafer hit a one-out double for the Brewers' first hit of the game, and after Wood struck out Estrada, Weeks continued his hot hitting. Weeks crushed a fastball out of the ballpark onto Waveland Avenue for a two-run homer to cut the Cubs' lead to 4-2.

NOTES: Brewers OF Carlos Gomez (sick) was not in the lineup Sunday. Manager Ron Roenicke said Gomez was either experiencing food poisoning or a stomach bug and wasn't feeling well enough to play. ... Milwaukee RHP Jim Henderson (right shoulder inflammation) threw a 25-pitch bullpen before Sunday's game at Wrigley Field. Henderson said the session was pain free and expects to throw another bullpen and have two to three rehab outings before coming off the DL. ... Both teams wore retro uniforms Sunday. The Cubs wore a throwback uniform from 1937, which was the year Wrigley Field's iconic scoreboard was installed and the ivy was planted. The Brewers also wore a 1937-inspired retro uniform.