Martinez was taking a flight from Austin to Seattle on Saturday night. Reliever Yoshinori Tateyama was optioned to Round Rock.
Napoli is listed as day to day after bruising the inside of his right knee in Friday night's win over the Seattle Mariners.
The injury, which probably occurred when Napoli was sliding into home plate in the fifth inning, was first listed as a bruised quad muscle, but Napoli said the pain is in the inside part of his upper right knee.
He was wearing a stretch bandage over it Saturday, but Rangers officials told Napoli he has no structural damage.
"It's sore and swollen," Napoli said. "I don't know how it's going to respond or what. I just have to get treatment and see what happens."
Rangers manager Ron Washington said he believes Napoli will be OK in a few days, but for now, the team had only one other catcher on the roster (Yorvit Torrealba) before recalling Martinez.
"Nap can catch if I really needed him," Washington said. "But I hope I don't need to and can give him some time. But it's not like a DL thing."
Rangers infielder Brandon Snyder has caught one inning this season and was the team's emergency catcher Saturday night until Martinez arrived.
"But that's a last resort," Washington said of using Snyder behind the plate.
When he first spoke with reporters Saturday, Washington said he talked to Rangers general manager Jon Daniels about whether they needed to bring in another catcher.
"It was discussed, but we felt it wasn't necessary," Washington said at the time.
Obviously, those plans changed. Martinez, 27, was hitting .262 at Round Rock with two home runs and 17 RBIs in 50 games. He played 22 major league games for San Diego in 2011, hitting .203.
Washington said he hopes to keep Napoli on the bench until Tuesday night at Oakland. The team has an off-day Monday.
"That's if everything falls into place, which you know rarely happens," Washington said. "Plans never work."
Napoli was asked if he could catch an inning if called upon to do so.
"If I had to," he said. "I can walk around OK, but I can't really squat down and bend my knee. I didn't really feel it when I was hitting (Friday night), only when I was catching."
Napoli stayed in the game Friday until the ninth inning when Torrealba replaced him behind the plate. Napoli also said Saturday he could pinch hit if needed.
Torrealba probably would have started Saturday's game against Seattle anyway because he caught the previous four games Yu Darvish started, and five of the previous six Darvish starts.
Darvish entered Saturday's game with a 4.57 ERA when Napoli was behind the plate and a 2.83 ERA when Torrealba was his catcher.