The Diamondbacks optioned Walston to Triple-A Reno on Wednesday.
The Diamondbacks activated Gallen (elbow) from the 60-day injured list Wednesday.
Walston (1-0) earned the win Tuesday against the Royals after allowing one unearned run while walking three and striking out two over two innings in relief.
Burnes didn't factor into the decision Tuesday against the Royals after allowing two hits and two walks while striking out two over three scoreless innings.
Carroll will be held out of the lineup again Wednesday in Kansas City and is scheduled to undergo imaging on his lower back Thursday when the Diamondbacks return home, Nick Piecoro of the Arizona Republic reports.
Jansen went 2-for-4 with a home run and four RBI in Tuesday's 10-5 win over the Mariners.
Lopez started at second base ans went 3-for-3 with an RBI and a run scored in Tuesday's 10-5 win over Seattle.
Jung (calf) went 2-for-5 with a double and an RBI for Triple-A Round Rock on Tuesday.
Nelson (elbow) struck out two and hit a batter over a scoreless inning for Triple-A Reno on Tuesday.
Tawa started in right field and went 3-for-5 with a home run and two RBI in a 5-3 extra-innings win over the Royals.
