Diekman cut the finger on a souvenir "Cheers" glass he bought when the Rangers were in Boston. He was unavailable during the club's four-game home series against the Twins, although Texas did not reveal the injury until Friday.
"It's more of a nagging deal on the top of his left index finger," general manager Jon Daniels said. "We hope to have him back in Kansas City."
Choo is day to day with tightness in his lower back, an issue he was dealing with in the final week leading up to the All-Star break. He had an MRI on Friday in Chicago.
"Same type of deal," Daniels said. "We don't think it's more significant and we're not worried about structural issues or a disk. [Choo is] frustrated it hasn't totally dissipated. He's probably day to day. We'll go off his symptoms."
The Rangers replaced Diekman in the bullpen by activating reliever Keone Kela off the 60-day disabled list. To make room for Kela on the 40-man roster, pitcher Derek Holland was transferred to the 60-day disabled list.
• Right-hander Kyle Lohse, who is dealing with a strained right oblique muscle, has been able to play catch, but the Rangers want to see him throw a bullpen session on Saturday before deciding for sure if he'll start on Tuesday against the Angels.
• Ryan Rua got the start in place of Choo on Friday, and first baseman Mitch Moreland was on the bench with no designated hitter being used in the National League park. Moreland has played the outfield in the past, but he has been dealing with a tight right calf muscle and the club doesn't want to risk any further injury.
• Kela hasn't pitched since April 19, and Rangers manager Jeff Banister wants to be reasonably cautious about how he uses the right-hander right away.
"He is not a six- or seven-year veteran," Banister said. "His first time out, we're not going to throw him out there in the ninth inning of a tie ballgame. But if we roll around to the seventh inning, we've got a lead and it's time to make a move, it's probably Kela."
• Texas signed 32-year-old outfielder Alexei Bell, a former Cuban National Series star, to a Minor League contract. Bell was a .319 hitter in the National Series from 2002-14, and he played on their '08 Olympic team and '13 World Baseball Classic team. He was playing in the Mexican League this season and he played in Canada last year.
• The Rangers signed left-handed pitcher Lucas Jacobsen, who was their 27th-round pick in the 2016 Draft out of Long Beach State. Friday was the deadline to sign Draft picks. Texas ended up signing 34 of its 40 picks.