And while Arias hit seventh Thursday against the A's, outfielder Josh Hamilton slid into Kinsler's usual three-hole in the lineup while Nelson Cruz moved up to fifth.
"We don't have Kinsler, so I'll put Hamilton back and try to get his bat up there at the plate as possibly as we can. Now Cruz can slip behind [Vladimir] Guerrero," Washington said.
It's a move that Washington said could potentially stick for the remainder of the season, but he noted that there's no way to tell right now.
"It could stick until Kinsler comes back. It could end up being [that] the rest of the year. I don't know, it's hard to call right now," Washington said. "When Kinsler comes back, he may need time to get himself together. So he may need to go down to the bottom of the order."
Washington said that Kinsler could likely still play instead of making an appearance on the disabled list, but he felt having Kinsler was more important down the stretch run than right now. Entering Thursday's game against the A's, the Rangers held a 7 1/2-game lead in the American League West.
"It's been going on for a while. It's been going on since before the All-Star break," Kinsler said of his injury. "It finally got to the point where I just needed to shut it down for 15 days."
"We have him down the stretch," Washington said. "We certainly don't want to get caught down the stretch like we did last year without Michael [Young], Hamilton, without Kinsler.
"He was disappointed. But we need him to play. We certainly don't need him to go out there with a strain, and it becomes a pull and it's worse. This way, we can get the 15 days and it's over with. At this time of the year, your body is broken down. It can be easy for something to get worse."
And while Washington believes Kinsler could play right now, he still thinks it's too serious of an injury to test.
"Anytime you strain a groin it's serious. That's why we decided to go to the DL," Washington said. "He's been playing with it. Yesterday, he just had some soreness there, so we decided to get an MRI. He said he's been feeling it for three days. But he's been able to with it. He probably could wrap it and go play. But this is too important. "
Added Kinsler: "It was never really intense. It was just kind of gradually getting worse. I don't want to pull it or tear it or anything like that."