After Sunday, that supposition should be put to rest.
McCarthy scattered nine hits in his first career complete game and the Rangers beat the Houston Astros 5-0 for a sweep.
"They talk about his stamina," Rangers manager Ron Washington said. "I think that question's finally answered."
McCarthy (4-2) struck out six and walked one while outpitching Mike Hampton (2-4).
McCarthy had pitched eight innings in a game in 2005, but had never gone the distance. He worked around a one-out single in the ninth, and needed seven pitches to strike out Michael Bourn to end it. McCarthy threw a career-most 124 pitches after throwing 118 in his last start.
"It's a confidence thing more than anything else," McCarthy said. "It's just knowing I can get through that deep in a game and still make quality pitches."
Miguel Tejada, who had four hits, doubled to put runners on second and third in the fifth before McCarthy retired Berkman to escape.
Washington said he was tempted to take McCarthy out before the ninth, but he was pitching so well he just couldn't.
"I didn't see any fatigue," Washington said. "You know, people change. This spring we wanted him to get in shape and show some stamina and that's what he's done."
Saltalamacchia was impressed with McCarthy's work.
"He threw all of his pitches and got ahead of hitters," the Texas catcher said. "That's the McCarthy I know. Before he was trying to make his pitches go to a certain place, but I told him: 'You just got to worry about attacking the hitters,' and he did that today."
Hampton, who has been bothered by a cut on his left thumb, allowed five runs and eight hits in five innings.
"No, it was not the finger," Astros manager Cecil Cooper said. "The finger was doing fine. He's not consistent in the strike zone like he needs to be."
Hamilton's solo home run to the Crawford Boxes in left field put Texas up 1-0 in the first.
Saltalamacchia pushed the lead to 5-0 with a solo home run in the fourth inning.
Bourn made a nifty play, chasing a long fly by Chris Davis up Tal's Hill in center field. He looked over his shoulder at the replay of the catch on the video board as he trotted back to his position.
Russ Ortiz allowed three hits and struck out one in four shutout innings for Houston.
Astros 3B Geoff Blum left the game in the seventh inning with a left hamstring strain and is listed as day to day. ... The Astros got a visit before Sunday's game from minor league catcher Jose Lopez, who is recovering from surgery to repair a brain aneurysm. Lopez, who played 39 games for Double-A Corpus Christi in 2008, underwent surgery on Thursday in Houston and received 36 staples to close the wound. The 24-year-old Lopez and his parents will remain in Houston until he is cleared for travel. ... Cooper said RHP Brandon Backe, who has been on the disabled list all season with a side strain, should pitch sometimes this week, but he isn't sure when. Backe said he isn't sure if he'll be in the rotation or working as a reliever.