MESA, Ariz. -- An A’s club that received some major reinforcements in the final weeks leading up to Spring Training saw the first appearance of the crown jewel of its free-agent signings on Tuesday.

Trevor Rosenthal -- whose one-year deal with the A’s was officially announced on Monday -- joined the A’s in camp for Tuesday’s workout. The right-hander attracted a good crowd for his first bullpen session and drew rave reviews from those who watched, manager Bob Melvin included.

“I thought I saw the ball a couple of times,” Melvin said. “It was more hearing it hit the catcher’s glove, to tell you the truth. Obviously, he’s got a powerful arm. We knew that coming in. But watching his delivery and how the ball jumps out of there, it just seems like it picks up speed all the way to the plate.”

Rosenthal -- whose fastball velocity ranked in the 99th percentile among Major League relievers in 2020 -- had no shortage of teams vying for his services this offseason. The clear opening for save opportunities following the departure of closer Liam Hendriks made Oakland an attractive option for Rosenthal. More important to him, though, was the excitement over this A’s team, which has reached the postseason in each of the past three seasons and continues to add pieces as they gear up to defend their American League West title in '21.

“The lineup is a powerful lineup, very dynamic speed and power and the things they can do on the field,” Rosenthal said. “Looking at the starting rotation, a lot of guys that are just starting to break out as well as some of the veteran mix, so it kind of checks all the boxes on paper. I think that's ultimately why the front office was comfortable making a lot of these moves to bring in some pieces to take us to the next level. That's really what I'm here for.”

Rosenthal has long admired the A’s for the way they always seem to have fun playing the game. The chance to be a part of that environment was also a factor in his decision-making process.

“This is a great franchise with a great history and a winning team that puts out a really competitive brand of baseball, an exciting brand of baseball,” Rosenthal said. “Looking at them over the years from across the field in the other dugout is something that's very attractive and appealing. When I got to that point of evaluating those things, it's something that I really wanted to be a part of and experience for myself.”

Just a couple of weeks ago, the A’s were unsure of how they might go about using their bullpen in the late innings. With Rosenthal’s arrival capping a recent string of reliever signings that also included bringing back Yusmeiro Petit and adding Sergio Romo, as well as trading for left-hander Adam Kolarek earlier this month, Melvin suddenly has a diverse group of arms who can serve as a bridge to Rosenthal.

“What a huge sign this is,” Melvin said. “Once you get the ninth inning nailed down, you can start looking at the other options and where everybody else fits in. Last year, our bullpen was one of the best in baseball. Now, it’s another fantastic bullpen with depth and a true closer. With Trevor here now, we know what the ninth inning looks like.”

Moreland signing official
The A’s officially announced the signing of slugger Mitch Moreland to a one-year deal on Tuesday. Paul Blackburn was designated for assignment in order to make room for Moreland on the club’s 40-man roster.

Moreland, who participated in Tuesday’s workout at Fitch Park, is likely to see most of his playing time at designated hitter with Matt Olson at first base. But regardless of what position he plays, the A’s know the impact Moreland makes at the plate, as he’s long tormented them over his 11-year career, with 22 home runs, 59 RBIs and an .859 OPS in 95 games against Oakland.

“We just keep adding good players,” Melvin said. “He’s just absolutely worn us out. I’m tired of watching him hit balls off that back wall in Oakland out in center field. We’re glad to have him. Another quality bat and a veteran guy that makes us a better team.”

Luzardo impressive on the mound
Partaking in his first live session against hitters this Spring, Jesús Luzardo appeared to be in good form. The left-hander’s first pitch hit 98 mph on the radar gun, and he generated several swing-and-misses, including one against new A’s shortstop Elvis Andrus to end his 30-pitch outing.

“Not the greatest draw for whoever was hitting in that group,” Melvin said. “Luzardo looked good right away.”

Right-hander Jeff Criswell, a second-round pick by the A’s last year who is ranked by MLB Pipeline as the club's No. 8 prospect, also looked sharp in his first session against hitters.

“Those are the kind of guys we’re trying to evaluate, and it looks like he’s got a live arm,” Melvin said. “He was throwing pretty hard, and it looked like he had better control of his breaking ball than he did in his bullpens.”