Pivetta has been a star in bullpen

That Nick Pivetta has pitched well in relief does not mean he should return to the Red Sox rotation. Quite the opposite: Stick with what works.

Pivetta has a 2.70 ERA and 11.3 strikeouts per nine innings over 12 appearances and 20 innings as a reliever this season. He had a 6.30 ERA and only 9.5 strikeouts per nine innings as a starter.

“He’s becoming a dude back there. His fastball is playing, the slider is good,” manager Alex Cora said. “He needed to go out there and become a solid reliever, and he’s become more than that.”

Pivetta didn’t agree with the decision to send him to the bullpen and even now only grudgingly acknowledges having pitched well.

“Things I’ve been working on have been paying off,” he said. “The team needs me in the bullpen and we’ve been doing a tremendous job back there. I think it’s a team effort.”

“Tremendous” is quite an exaggeration considering Sox relievers are 11th in the American League in ERA (3.94), 11th in WHIP (1.31), and 14th in strikeouts per nine innings (8.0).

But Pivetta is throwing more strikes and has better fastball velocity. If the Red Sox trade Kenley Jansen, he’d be a good candidate to close.

A few other observations on the Red Sox:

■ Jansen appeared in only 28 games and threw 26‚ innings in the first half.

That’s his fewest for a full season since 2015, when he spent nearly seven weeks on the injured list to open the year. Jansen averaged 37.3 appearances and 38„ innings in the first half from 2016-22, discounting the 2020 season.

The Sox gave Jansen $36 million over two seasons. So far it has been for cameos.

■ Whatever your defensive metric of choice is, Triston Casas grades out poorly at first base.

He’s minus-5 in defensive runs saved and outs above average and is tied for sixth in the majors in errors.

Casas has too much faith in his range, all too often drifting to his right to chase a ball the second baseman is better positioned to handle.

“A step slow,” one scout said. “He hesitates and goes, and by then it’s too late.”

Casas played 284 games in the minors, 242 of them at first base at five levels. Presumably, he should have arrived better prepared.

A bigger question is whether Casas understands the need to improve. His confidence in his defense — “My footwork is immaculate,” he said last month — is more hubris at this point.

Casas has shown improvement at the plate, but his .404 slugging percentage is still 17 th among 25 qualified first basemen.

Casas was a celebrated prospect and he’s only 23, so he should get plenty of runway. But at the moment he’s a poor defensive first baseman who doesn’t hit for much power.

■ Remember when the Sox gleefully touted Kiké Hernández as a pivotal first step to their rebuild when he was signed to a one-year, $10 million extension last September? Hernández’s minus-0.5 bWAR this season is the lowest of his career and he has a .629 OPS over the last two seasons.

■ Righthander Noah Song pitched in his first minor league game for the Phillies on Wednesday and threw a perfect inning with one strikeout for Single A Clearwater.

In his first game since 2019, the 26year-old former Red Sox prospect hit 93.5 miles per hour with his fastball and threw 7 of 12 pitches for strikes.

Song is on an injury rehab assignment that can last 30 days. At that point, the Phillies would have to add him to their major league roster or place him on waivers and offer him back to the Red Sox.

Dave Dombrowski didn’t come this far to let Song slip away. The Phillies will work hard to find a way to keep him.

■ It cost the Red Sox $63 million to sign infielder Yóan Moncada in 2015 — $31.5 million for his signing bonus and a $31.5 million penalty paid to Major League Baseball for exceeding the rules at the time regarding international players.

In retrospect, it was not a waste of money. Moncada was the big chip that helped the Red Sox trade for Chris Sale in 2016, and Sale helped deliver the 2018 World Series championship.

That trade turned out to be a break in other ways, too.

Moncada had a .799 OPS and 8.3 WAR over 335 games prior to agreeing to a five-year, $70 million extension with the White Sox. He has a .710 OPS and 5.4 WAR over 338 games since.

Moncada hasn’t played since June 13 because of lower-back pain and isn’t expected back any time soon.

Back in 2015, Moncada was supposed to be a superstar. He turned out to be a little better than league average as a hitter, a little below as a defender.

■ The Red Sox should do Bobby Dalbec a favor and trade or release him. Dalbec, who has a 1.051 OPS in Triple A, was called up for three games and given one plate appearance.

If the Sox have no use for Dalbec, let him take a shot somewhere else.

■ The Red Sox are 2-13 against National League teams (Cardinals, Marlins, Pirates, Reds, and Rockies) at Fenway this season and have been outscored by 30 runs.

■ Ken Rosenthal of Fox Sports and The Athletic picked an All-Star roster and included only Alex Verdugo from the Red Sox.

Verdugo or Rafael Devers would be acceptable choices. It doesn’t seem likely the Sox would merit a second AllStar. The team will be announced Sunday night.

The Sox haven’t had just the one mandatory All-Star since Brock Holt in 2015.