"I feel good," Diekman said. "I don't know how my arm strength is, but I feel good."
The Rangers will see how Diekman recovers from the session before they determine his next step. He could get another batting practice session, or he could be assigned to the Minor Leagues on a medical rehabilitation assignment.
Diekman said he is ready for a rehab assignment, but pitching coach Doug Brocail said that is still to be determined.
"I want to see how he responds and get everybody's opinion," Brocail said. "I'm not putting a timeline on this. I want to make sure we get this thing right."
Diekman pitched to Ryan Rua, Mike Napoli and Drew Robinson. He wasn't expected to throw as many as 31 pitches, but the goal was to push him physically so they can see how he responds from the session.
"I need that arm to get tired so we can build it back up," Brocail said.
Rangers trade for slot money: The Rangers have acquired an extra $500,000 in international bonus pool money from the Orioles in exchange for Minor League infielder Brallan Roberts.
The Rangers were allotted $4.75 million for the yearlong international signing period that began in July, but are allowed to add to it through trades with other clubs not interested in spending their allotments. They have already done so: twice in trades with the Orioles and once with the White Sox for Minor League infielder Yeyson Yrizarri.
Perez, 21, was signed out of Colombia in 2012 and was not among the Rangers' Top 30 prospects. He was hitting a combined .270 at Class A Hickory and Class A Advanced Down East this season.
• Nick Martinez turned 27 on Saturday, on the eve of starting against the Twins on Sunday.
• Carlos Gomez was given a day off on Saturday as Robinson made his second start in center field. Manager Jeff Banister said this was a planned day off for Gomez.
• Reliever Keone Kela went into Saturday's game having held opponents to a .128 batting average. That was the lowest among qualifying relievers in the American League.
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.