After that, however, Mock settled down. He allowed just one run over the rest of his outing and left the game after six innings, striking out eight. After the game, Manny Acta praised Mock's improved poise and his ability to adjust after a rough first inning.
"I think the difference today was he was able to throw his breaking ball for strikes," Acta said postgame. "After that first inning, he put it back together and gave us a good effort. We were very happy."
After the game, Mock was harder on himself for his rough first inning than he was happy about his last five. He said he was particularly disappointed with the way he pitched David Murphy in the first, who had the bases-loaded double that scored two runs.
"I think that kind of changed the complexion of the game," Mock said. "If I had executed the pitch and gotten the third out of the inning, only one run scores. Then the team doesn't have to tighten up and scratch and claw for runs like they did."
The Nationals tried to fight back, slowly chipping away at the Rangers' lead for the first half of the game. Lastings Milledge pulled a run back with a solo homer to left in the fourth inning. Dmitri Young doubled in the next at-bat, then moved to third and scored on a pair of groundouts by Ronnie Belliard and Felipe Lopez.
The Nationals played more small ball an inning later to score Wily Mo Pena, who reached on a single. Pena took second on Mock's bunt, moved to third on a Cristian Guzman single and scored on a ground-ball double play off the bat of Elijah Dukes, pulling the score to 4-3.
Washington threatened to take control of the game from Texas in the bottom of the sixth, loading the bases with only one out. But Pena flew out to center and pinch-hitter Kory Casto lined to short on successive at-bats, ending the inning.
The Rangers delivered the final blows in the following frame, sending 11 batters to the plate and plating seven runs to move the score to 11-3 right before the seventh inning stretch. Runs in the eighth and ninth would leave the final at 13-3.
Though Mock picked up the loss, Acta said he liked what he saw from the young Texan. He said he saw improvement over Mock's first Major League appearance, in which the right-hander lasted just 4 1/3 innings and gave up four runs.
"I like what I see," Acta said. "I like his confidence. He's tough."
Despite his early struggles, Mock did say he would take plenty of positive lessons away from his second start in the big leagues.
Catcher Paul Lo Duca, who settled in behind the plate for the first time since returning from injury, said Mock impressed him with his confidence and his ability to adjust on his own. He said Mock recognized when he made mistakes and showed off an impressive breaking ball, reasons Lo Duca thinks Mock has a bright future.
"I think he showed that he can belong here," Lo Duca said. "He impressed me a little bit. He beared down and didn't let that first inning bother him and really threw the ball well."
Zach Osterman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.