MESA, Ariz. -- Long praised for his defensive prowess in the Minors, Jonah Heim is really just a slight uptick in offensive production away from punching his ticket to the Majors.

With expected Opening Day catcher Sean Murphy not expected to play in Cactus League games until March 2 as he eases his way back from offseason knee surgery, Heim, the A’s No. 21 prospect, per MLB Pipeline, has a golden opportunity in front of him with extra playing time as he battles newcomer Austin Allen for the backup catcher job.

“We’ve had some experience with him in camp, but he never got to play a whole lot. That’s going to change here,” A’s manager Bob Melvin said of Heim. “Last year, speaking to the guys in development, that was a breakout year for him. Body language, everything that a catcher has to portray, he’s taken significant strides with that. Every pitcher that’s thrown to him really enjoys throwing to him. He looks confident.”

The bat looked sharp in Saturday's 12-2 loss to the Cubs in the Cactus League opener, as Heim roped a single to right field in his first at-bat off Cubs reliever Duane Underwood Jr. as part of a 1-for-2 night. The much-hyped defense was also on display in the third as he made a nice stop on a pitch in the dirt from reliever Miguel Romero before firing a bullet of a throw to Franklin Barreto for an easy putout of Jason Heyward, who was trying to take second base.

“He was real calm back there. Got all the signs I gave him. He had a lot going on back there with their guys swinging the bat well,” Melvin said. “For a first start, you would think a guy like that has some nerves, but he certainly didn’t show it."

Heim’s bat may be a bit further along than the rest of the catchers in camp this spring. After a solid 2019 campaign in which he slashed .310/.385/.477 over 85 games combined at Double-A and Triple-A, Heim continued his season into the winter by playing for the Toros del Este in the Dominican Winter League. The 24-year-old catcher also found success at the plate there with a .301/.386/.411 slash line in 20 games.

Heim played the first six innings at Sloan Park on Saturday before he was replaced by Collin Theroux. Allen, who was acquired from the Padres in exchange for Jurickson Profar during the offseason, entered the game in the sixth as the designated hitter and went 0-for-2 with an RBI.

With the A’s only expected to carry two catchers on the roster, Saturday marked just the beginning of what should be an interesting battle between rookies for the role.

“We have some competition for the backup spot,” Melvin said. “Jonah had a really good year last year and I don’t think Austin wants anything handed to him. Obviously, we traded a pretty good player for [Allen]. We wanted some catching depth.”

Puk impresses in debut

Things couldn’t have gone much better for A.J. Puk in his Cactus League debut. Slotting into the starting rotation this season after a brief 2019 cameo out of the bullpen, Puk looked sharp in a scoreless first inning against the Cubs. The left-hander threw 13 pitches, nine for strikes, including a three-pitch strikeout of Kris Bryant with an 87 mph slider dropping in for strike three after two fastballs clocked at 95 and 97 mph.

“It was great to be back out there and start a game again,” Puk said. “I was real happy with the results other than the two-out walk to [Javier] Báez. If I would have landed my 0-0 curveball to Báez, it would have been a perfect outing. But it was good.”

After being limited to just his fastball and changeup for most of 2019 in an effort to protect his arm as he returned from Tommy John surgery, Puk is now free to unleash his curveball and changeup, as well. He threw all four pitches on Saturday night.

“The changeup that he didn’t have last year, that’s what is going to make him who he is,” Melvin said. “His fastball even plays up because of it. He looked really good.”

Second-base battle underway

In addition to the competition at catcher, there’s also a five-man battle going on for the starting job at second base. Jorge Mateo and Barreto were the focus of the battle on Saturday as both started. Mateo played short and Barreto played second, each going 1-for-3 with singles. Vimael Machin, also in the second-base mix, replaced Barreto in the sixth and flied out in his one at-bat.

“They were out there a little longer than everybody else because we want to see them get some at-bats,” Melvin said of Mateo and Barreto. “It’s too early to really tell there. They’ll get plenty of at-bats.”