CINCINNATI — Johnny Cueto wasn’t going to let a blister sidetrack the Cincinnati Reds’ best run in four years.

Cueto threw six shutout innings despite a blister on his pitching hand Thursday night, and Scott Rolen hit a three-run homer during an early splurge off Charlie Morton — the major leagues’ leader in losses — for an 8-2 victory over the Pittsburgh Pirates.

The NL Central leaders have won 21 of their last 30 games, moving a season-high eight over .500 at 28-20. They haven’t been that well off since 2006, also was the last time they were in first place so deep into a season.

Their main concern was Cueto (5-1), who had to leave a win in Cleveland last Saturday after six innings because of a blister on his right index finger. Given a big early lead, he could afford to ease through six shutout innings. He gave up three hits and struck out a season-high nine while winning his fourth straight start.

“We took him out primarily as a precaution with the blister,” manager Dusty Baker said. “They’ve been treating it. They’ve been putting all kinds of stuff on it. It bothered him some on his slider, so he didn’t throw too many sliders. He’ll be ready and 100 percent for his next start.”

Cincinnati’s offense made it easy for him.

The Reds batted around in each of the first two innings for seven runs off Morton (1-9), who had his second-shortest start of the season. The first two innings lasted 59 minutes, with Morton throwing 68 pitches in all. With an ERA of 9.35, his job is in jeopardy.

Manager John Russell met with Morton in his office for about 20 minutes after the game. Asked if Morton was still in the rotation, Russell said, “As of now, yeah.”

“He’s had some shoulder fatigue, but he’s been fighting through it,” Russell said. “In his last couple of starts, he’s felt a little bit of pain, fatigue. But he seemed to throw the ball pretty firm tonight. It was a good sign. We’ll have to keep evaluating him. You hate for one start to kind of negate the little bit of progress he was making. He was making some — not great.”

Morton knows that he won’t be in the rotation much longer if he doesn’t get much better.

“I think we have plenty of talent in the system,” Morton said. “Every time I’ve had a bad start, I know that there are other options. It’s not something that I’m not aware of, not something that I don’t think about. It’s the reality of the game.”

The Reds took three of four from the Pirates, who had no chance after Morton had another meltdown. Pittsburgh lost 4-0 on Wednesday night — the eighth time the Pirates were blanked this season, most in the majors — and their scoreless-innings streak reached 15 a day later. Aki Iwamura ended it with a pinch-hit, RBI single in the seventh.

Rolen’s three-run homer snapped a personal 0 for 11 skid and extended one of the best power streaks in club history. Cincinnati has homered in its last 16 games, the best in the majors this season. The streak is tied for fourth-longest in Reds history — the 1956 club homered in 21 straight for the record.

Jay Bruce followed with his first homer since April 29, a sign that things weren’t going to get any better for Morton.

The Pirates’ best hope was that Cueto would have more problems with the blister on his right index finger. It hardly made a difference.

“I felt a little pain,” Cueto said. “Right now, it’s painful. The last inning, it burned a little bit.”

Cueto threw a one-hitter in Pittsburgh on May 11 for a 9-0 win, with Ronny Cedeno’s single off shortstop Paul Janish’s glove going for a single. In the rematch, he allowed two singles by Jeff Clement and a double by Cedeno. In his last four starts, Cueto is 4-0 with a 1.09 ERA.

NOTES: The Pirates headed for a weekend series in Atlanta. … 3B Andy LaRoche was back in the lineup after missing five games with a sore back. He had a throwing error that prolonged the second inning. … Neil Walker, called up on Tuesday, made his first start at 2B, a position he learned during spring training. … The Reds plan to promote RHP Sam LeCure from Triple-A Indianapolis to start on Friday in the series opener against Houston. LeCure will make his major league debut, filling in for RHP Homer Bailey while he recovers from an inflamed pitching shoulder. … 1B Joey Votto missed his second straight game with a sore neck.