On a day the A’s would like to quickly forget (as they were on the wrong end of a 10-3 loss to the Royals in Surprise, Ariz.), Monday's biggest development came off the field.

Following the game, A’s manager Bob Melvin revealed that new A’s closer Trevor Rosenthal is dealing with a slight groin strain. Rosenthal, who had been throwing bullpen sessions on a regular schedule at the club’s training complex in Mesa, Ariz., began to feel the discomfort on Saturday.

Rosenthal was originally scheduled to make his spring debut on Monday against the Royals. Melvin said while the injury is not believed to be too serious, there is no timetable for Rosenthal’s return to the mound.

“We don’t have a target date for him to throw yet,” Melvin said. “We think it’s minor in nature, but you want to be pretty careful with those types of injuries. He’s been feeling it the last two days.”

Rosenthal, who signed just days after the A’s opened up camp, is expected to take over the closer role that was previously occupied by All-Star Liam Hendriks, who signed with the White Sox as a free agent on Jan. 15. The 30-year-old right-handed Rosenthal is coming off an excellent 2020 campaign, having combined for a 1.90 ERA with 11 saves and 38 strikeouts across 23 2/3 innings with the Royals and Padres last season.

Allen continues to see playing time
The absence of Minor League games last year makes this spring an important one for many A’s prospects on the cusp of the big leagues. That’s why Nick Allen, Oakland’s No. 4 prospect per MLB Pipeline, continues to see plenty of action early in the Cactus League schedule.

After starting Monday’s game at shortstop, Allen, 22, has now played in seven of eight games this spring for the A’s.

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“That’s another downside to not playing nine innings; some of these guys didn’t get to play last year,” Melvin said. “This spring is important for [Allen]. He’s a top prospect of ours, and we want to take a hard look at him. We’re not going to run [Elvis] Andrus out there too much early on, so it’s a great opportunity for him.

“He looks eager to play. This is a time that we’re looking at a lot of our top prospects, and he’s embracing it.”

Ranked as the top defensive shortstop prospect in baseball entering 2021, Allen’s defense appears ready for the big leagues. It’s his bat that needs some fine-tuning, and he will get a chance to work on that this year as he’s likely to begin the season at Double-A Midland. Allen showed improvement at the plate in '19, hitting .292 with 22 doubles while swiping 13 bases in 72 games with Class A Advanced Stockton. Those improvements carried over to the club’s alternate training site in San Jose, Calif., last summer, according to A’s farm director Ed Sprague.

“It’s not out of the realm of possibility that Nick gets an opportunity [in the Majors] this year,” Sprague said. “In a perfect world, we’d like to get him a few hundred Triple-A at-bats to see how he does. He hasn’t played above A-ball. But he’s polished defensively and probably ready for the Major Leagues there.”

Up next
The A’s travel to Sloan Park in Mesa, Ariz., for a 12:05 p.m. PT game against the Cubs on Tuesday. Left-hander Cole Irvin will make his second start of the spring in a game that is expected to feature the debut of Jed Lowrie, the former All-Star second baseman who is back with the A’s on a Minor League deal and looking to earn a third stint with Oakland. Lowrie was held out of games earlier in the Cactus League schedule as he returns from offseason surgery on his left knee.

Right-hander Sergio Romo is also expected to make his A’s debut, with left-hander Adam Kolarek and righties Burch Smith and Brian Schlitter also available to pitch.