Milwaukee's rotation has been outstanding. The starters have a combined 1.80 ERA over the first 12 games, giving up just 22 earned runs.
Lohse said he was disappointed to be pulled one out from a complete game, but understand the decision by manager Ron Roenicke.
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"It is tough, but I understand," he said. "I've been around long enough to know that we need to win that game and keep the momentum going. I wanted to finish it, but I know that if I wanted to I needed to get that guy (McCuthchen) out."
Roenicke said he pulled Lohse because he was at 100 pitches.
"Sometimes the decisions aren't very popular, but they're decisions as a manager you need to make," Roenicke said. "I thought Kyle pitched a great game. When you get to 100 pitches, that starts to put pressure on a pitcher and we've got a long season to go."
Lohse had some fine defense behind him as shortstop Jean Segura made several tough plays and outfielder Logan Shafer robbed Alvarez of at least a double in the second inning when he hauled in Alvarez's long drive just before crashing into the left field wall.
"That was huge because normally that is a double and then I have some work to do," Lohse said.
The Brewers broke open the game in the sixth, helped by an error. Aramis Ramirez walked and moved to third on Lyle Overbay's double, just his second hit of the season.
Morton struck out Scooter Gennett, but the ball was in the dirt. Catcher Tony Sanchez's throw to first was wide and went down the right field line, allowing Ramirez and Overbay to score.
Roenicke said the play was an example of all the breaks the Brewers are getting right now because the team is playing well.
"I think anytime you play good baseball and are doing things right, you seem to get more breaks," he said. "They make that play and we have to come up with big hits in other places."
Charlie Morton (0-1) pitched seven innings as the Pirates lost for the fourth time in five games.
"It would have been a much closer game if I didn't butcher that play," Sanchez said. "I take a lot of pride in my defense and I take a lot of pride in getting my pitchers through as many innings as possible. That score does not reflect Charlie's performance today."
Martin Maldonado got the first hit of the game as he lined a double off the right field wall leading off the Milwaukee third. Lohse sacrificed and Carlos Gomez hit a sacrifice fly.
The Pirates tied the game in the fourth. Starling Marte led off with a single, moved to third on a perfect hit-and-run single by Jose Tabata and scored on McCutchen's sacrifice fly, just beating the throw from Gomez in center.
Ryan Braun doubled in the Milwaukee fourth and scored on a single by Ramirez, who has 11 RBIs.
The Brewers will try for their 10th straight win Monday night when they host St. Louis. Matt Garza starts against the Cardinals' Lance Lynn. ... The Pirates move on to Cincinnati, where Wandy Rodriquez will face Homer Bailey of the Reds. ... The Brewers and the Pirates will meet again in a four-game series in Pittsburgh starting Thursday.
Copyright by STATS LLC and The Associated Press
MILWAUKEE, WI - APRIL 13: Charlie Morton #50 of the Pittsburgh Pirates pitches during the bottom of the second...
32,152 (76.7% full) - % is based on regular season capacity
Home Plate - Vic Carapazza, First Base - Adam Hamari, Second Base - Greg Gibson, Third Base - Bill Miller
How Kyle Lohse beat the Pirates
* Pirates were 0-8 with 3 K in AB ending in slider
* Generated 10 swings and misses with slider, T-2nd most in any start since 2009 (took 20 swings vs slider total in game)
* 23 1st pitch strikes, T-2nd most in any start since 2009
* Pirates were 3-20, 7 K after being down 0-1; 3 balls put in play on 1st pitch (0-3)
The Brewers 10-2 start is their 2nd-best 12-game start in team history. They started 12-0 in 1987 (eventually evolved to 13-0)