The Pirates went ahead when Russell Martin followed by hitting a grounder up the middle that Segura, the shortstop, misplayed for an error, allowing Snider and Cole to score. McCutchen and Alvarez followed with RBI singles to knock the 6-foot-9 Hellweg from the game.
"We had some trouble with (Hellweg) in the first inning," McCutchen said. "He's so big and he was throwing sinkers from a downhill angle at a time when there still were shadows on the field. Then we got adjusted to him."
Milwaukee acquired Hellweg and Segura, who leads the National League with 104 hits, last July from the Los Angeles Angles in a trade for ace pitcher Zack Greinke. Hellweg was 7-4 with a 2.82 ERA in 14 starts with Triple-A Nashville this season.
"I wanted to have a good pace, I thought that was important in my first game, but I really started rushing things, especially in that second inning," Hellweg said.
The Brewers jumped on Cole for three quick runs.
A walk to Norichika Aoki and singles by Segura and Gomez loaded the bases and Aramis Ramirez walked to force in a run. A second run scored when Jonathan Lucroy grounded into a double play and Francisco capped the inning with an RBI single.
However, the 3-0 lead held up only for one inning, and the Pirates added on runs following their seven-run second. Marte hit an RBI double in the third and tripled in the sixth and scored on McCutchen's double. McCutchen homered off Michael Gonzalez in the eighth.
"I was on the ropes and the pitch count was getting up there in that first inning but I got some groundballs in the second, guys made some really good plays behind and that settled me down," Cole said.
NOTES: Brewers 1B Corey Hart will miss the season. He is scheduled to have surgery to repair cartilage damage in his left knee July 26. Hart has been on the disabled list all season after having right knee surgery in January. ... Snider left the game after six innings with a bruised right foot. ... Milwaukee activated RHP Hiram Burgos from the 15-day disabled list and optioned him to Triple-A Nashville. ... The Pirates recalled INF/OF Josh Harrison from Triple-A Indianapolis and optioned C Tony Sanchez to the same club. ... Milwaukee RHP Donovan Hand (0-0, 2.37) faces Pittsburgh LHP Francisco Liriano (6-3, 2.30) on Saturday night.