Tomas came up to the plate for the first time in the second inning and grounded out to second base.
"With the bat, I thought this was how he would look," D-backs manager Chip Hale said. "He looked very comfortable. He looked very relaxed."
Then in the fifth, Tomas singled up the middle against David Graybill.
"The first ball, [he] hit a nice hard ground ball to second. That's the approach we want from him," Hale said. "And then to hit that ball right back up the middle, that's a beautiful thing."
Much has been made of Tomas' transition from the outfield, where he spent most of his time playing in Cuba, but his first test will have to wait, as he did not have a ball hit to him in his five innings.
"What are you going to do?" Tomas said. "You can't control that, but there will be plenty of opportunities for the ball to come and me to get it."
The D-backs did move him around as far as his positioning at third base, and he got a taste of running the bases after his single. He advanced from first to third on a single by Tuffy Gosewisch and then got caught in a rundown when Nick Ahmed hit a grounder to third baseman David Greer.
Getting in the rundown was actually the proper play, because there was also a runner on first, so rather than have the Sun Devils turn a double play, the runner on third should break for the plate to draw the throw there.
Tomas is not scheduled to be in the starting lineup for Wednesday's Cactus League opener against the Rockies, but he should see some time at third in relief of Jake Lamb.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.