"The injury that Lamb has is not good, because he's really important for the team," Tomas said. "I'm going to be ready for any responsibility that they give to me. My goal is to try and do the best that I can in the game."
Tomas singled to right in the second inning, grounded out to short in the fourth and legged out an infield hit deep into the hole at short in the sixth.
"He had three good at-bats, put the ball in play, got two hits," D-backs manager Chip Hale said. "We know what we have. We know he can hit. We just need to find some at-bats for him. His opportunity is here for him to play and get some at-bats. We'll see how he does."
While Hale said the club sees Tomas' long-term future as being in the outfield, he could get some regular time at third.
Tomas' error came in the third when he tried to backhand Elvis Andrus' grounder on a short hop.
"He just didn't move his feet," Hale said.
Tomas picked up his first Major League hit Sunday in San Francisco and is 3-for-7 since being called up early last week.
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.