Gallo has been dealing with the hamstring injury since Spring Training, but he said it really has become an issue in the last few weeks. He missed two games on June 24-25 and two more on July 7-8 in Arlington before playing in the final game before the All-Star break. He was not in the starting lineup on Saturday because tough left-hander Danny Duffy started for the Royals.
Gallo entered Saturday's game hitting .192 with 21 home runs, 41 RBIs, a .311 on-base percentage and a .504 slugging percentage. He led the team with 113 strikeouts, but he was also second with 39 walks.
The hope is the numbers get better in the second half as Gallo gains experience and starts getting more familiar with American League pitching.
"Hopefully it will make a big difference when you start to face these teams the second and third time through," Gallo said. "I feel more comfortable, able to get deeper in the counts and be patient. That's the one thing I want to be good at. I feel like I'm being patient and controlling the at-bat. If he doesn't throw strikes, I'm taking more walks."
Right-hander A.J. Griffin, on the disabled list with a strained left intercostal muscle, began a medical rehabilitation assignment by pitching three scoreless innings for the Arizona Rookie League Rangers on Friday.
Griffin faced nine batters in an outing against the Athletics and struck out two. It was his first time in a game since May 26 in a start against the Blue Jays.
Griffin is on the 60-day DL, which means he is not eligible to be activated until at least July 26. He will likely need at least two or three more Minor League outings before he is an option at the Major League level.
• Entering Saturday's game, the Rangers had scored 49.7 percent (223 of 449) of their runs on home runs, including all five on Friday night. That was the third highest behind the Blue Jays (52.5 percent) and the Athletics (49.9).
• Right-hander Nick Martinez threw six scoreless innings for Triple-A Round Rock on Friday night. He allowed just one hit and two walks in his second start since being sent down before the All-Star break.
• Friday's 5-3 victory over the Royals marked the first time this season the Rangers have won a road game despite trailing by as many as three runs at some point.
• The Rangers sent Minor League infielder Yeyson Yrizarri to the White Sox for international slot compensation. The move gives the Rangers extra money beyond what is allotted by Major League Baseball to continue to be aggressive for international free agents.
T.R. Sullivan has covered the Rangers since 1989, and for MLB.com since 2006. Follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.