Maybe it was the adrenaline of making his first start this season in the majors. Or maybe, as Spencer Howard suggested Saturday night, he didn’t take enough time to slow his heart rate after running to first base for the final out of the second inning.

Whatever the case, the Phillies are looking for answers to explain why the young right-hander’s average fastball velocity fell from 96.2 mph in the first inning to 93 mph in the third.

“We’ll have to poll the audience and talk to as many people as we can to help him get over the hump,” pitching coach Caleb Cotham said before Sunday’s game at Citizens Bank Park. “We’re trying. He’s trying. We feel confident that we can give him tools and techniques to manage the game the day of the game.”

Cotham was pleased overall with Howard, who gave up two runs on one hit, four walks, and one hit batter in three innings against the Boston Red Sox. In particular, Cotham liked how Howard’s bat-slowing changeup paired with his fastball and the shape and depth of his slider.

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Howard’s next start is scheduled for Thursday in Miami. It’s unclear how much, or even if, the Phillies will allow him to build on his 68 pitches against the Red Sox. After shoulder problems limited Howard’s workload in each of the last two seasons, they’re trying to figure out a way to have him pitch meaningful innings while also getting him through as much of the season as possible without risking overuse.

Cotham said the Phillies have studied examples of other pitchers who were brought along gradually at the major-league level and picked up “breadcrumbs” from each case. He noted the Baltimore Orioles’ usage of Dylan Bundy in 2016.

Bundy, then 23, missed parts of three seasons because of Tommy John elbow surgery and a shoulder problem. He began the 2016 season in the bullpen, but moved into the rotation in July and threw 71⅔ innings over 14 starts. He pitched 109⅔ innings overall for an Orioles team that went to the playoffs as a wild card.

Howard has thrown 16⅓ innings so far this season between triple A and the majors.

“I don’t think you can expect him to go six, seven [innings] on turn the rest of the season,” Cotham said. “But we want him pitching meaningful innings and we want him helping the team. I think every situation is different. The one that sticks out is kind of how the Orioles handled Bundy. I don’t know if there’s a perfect answer, but you do look at those and how those went.”

Day off for Harper

Bryce Harper, 0-for-16 with one walk and 10 strikeouts in his last four games, wasn’t in the lineup Sunday. With a chance to pad the lead in the eighth inning and the pitcher’s spot due up, Harper wasn’t used as a pinch-hitter.

What gives?

“It was just a day off,” manager Joe Girardi said.

Pressed about whether Harper’s sore shoulder acted up again, Girardi reiterated that it was “just a day off.”

» READ MORE: Injuries are spiking across MLB this season. What can the Phillies do to survive? | Scott Lauber

Extra bases

Shortstop Ronald Torreyes made a throwing error and third baseman Alec Bohm dropped a foul pop in the ninth inning, giving the Phillies 13 errors in their last nine games. ... Reliever Archie Bradley allowed a ninth-inning solo homer on a 91 mph fastball. ... The Phillies claimed right-handed reliever Brady Lail off waivers from Seattle and optioned him to triple-A. Lail, 27, has a 6.00 ERA in 11 major-league appearances, all with the Mariners. Right-hander Ramón Rosso was designated for assignment to open a spot on the 40-man roster. ... Triple-A infielder Luke Williams was named to Team USA’s 28-man training-camp roster for the Olympics qualifying tournament. The camp will be held this week, with the tournament beginning May 31 against Nicaragua in Port St. Lucie, Fla. The 26-man roster must be finalized by Sunday. Former Phillies reliever David Robertson is also trying to make the team, which will be managed by longtime former Angels manager Mike Scioscia. Williams is batting .368 with a .927 OPS for Lehigh Valley. ... Zach Eflin will start the series opener Monday night in Miami against Marlins lefty Trevor Rogers, who held the Phillies to one run on five hits in 7⅔ innings last week.