"I just tried to keep a straight face because my teammates were all like, 'What just went on in there?'" Grimm said.
After Washington declared Grimm the starter for Saturday, Grimm talked to his family, packed his stuff and prepared to head south to Arlington. He'll make his Major League debut against the Astros in front of a likely sellout crowd at Rangers Ballpark in Arlington.
Grimm, a right-hander, said getting called up this season was always in the back of his mind.
"If it's not, you shouldn't be playing," Grimm said.
He takes over for Alexi Ogando in the rotation. Ogando, who originally replaced Derek Holland in the rotation, is on the 15-day disabled list with a strained right groin suffered Sunday.
The Rangers will likely purchase Grimm's contract from Frisco on Saturday. At Double-A, he was 8-3 with a 1.87 ERA and 67 strikeouts. His ERA is the 11th-lowest in all of the Minors.
A fifth-round selection in the 2010 First-Year Player Draft, Grimm will wear No. 51. Washington said the Rangers won't burden Grimm mentally heading into his first start.
"He's here because we believe he can handle the situation," Washington said.
The Astros counter with Lucas Harrell, a pitcher considered a rookie even though he pitched in the Majors in 2010 and '11. With 76 1/3 innings, he ranks first in the National League in innings among rookies and second in the Majors, behind the A's Tommy Milone.
Against the White Sox -- his former club -- on Sunday, Harrell went 7 1/3 innings, giving up five runs on six hits. He has thrown more than five innings in his last 11 starts.
"I gave up a few hits in situations, but we had the lead and I controlled the damage and the guys scored enough runs for us to win," Harrell said.
Harrell relies on the ground ball for outs. His ground-ball/fly-ball ratio is 2.39, the sixth-highest in the Majors.
Luck has been on Harrell's side recently. His ERA in his last five starts is 5.46, but he is 4-1 over that span.
Rangers: Hamilton likely to sit out series
Center fielder Josh Hamilton sat out Friday's game after being hospitalized with an intestinal virus on Friday morning.
Manager Ron Washington doesn't expect Hamilton to play Saturday, either. Hamilton's status for Sunday is questionable, though Washington doubts Hamilton can be fully healthy in time for the matinee series finale.
Hamilton left Thursday's game against the D-backs after complaining of a stomach ache. Hamilton's wife and daughters have both been sick recently.
The Rangers brought Leonys Martin up from Triple-A Round Rock to play center field. He batted ninth and went 0-for-3 with a walk on Friday. To clear space for Martin, the Rangers sent pitcher Koji Uehara to the disabled list with a strained right lat muscle.
To activate Grimm, the Rangers will need to make another roster move.
Hamilton is hitting .330 with 22 homers, 66 RBIs and a .674 slugging percentage.
Astros: Norris unlikely to start Sunday
Bud Norris, who sprained his left knee in his last start on Tuesday against the Giants, probably won't pitch on Sunday, his scheduled slot in the rotation.
Manager Brad Mills said the Astros will wait to see if Norris' condition improves on Saturday.
"We're hoping things turn for the better and we're able to work things out," Norris said. "Obviously, we need to make that decision here pretty quickly, and we will [Saturday] at some point."
Mills said Norris, who won't comment on the injury, felt a little tentative on the knee in a bullpen session on Thursday in San Francisco.
The Astros list Sunday's starter as TBA.
There are standing-room tickets available for Saturday's game and 1,000 reserved seats available for Sunday's game. Once Sunday's reserved tickets are sold, the Rangers will put obstructed view and standing-room tickets up for sale.
Astros shortstop Jed Lowrie walked in the first inning to end the Rangers' six-game streak of three-up, three-down first innings.
Hamilton's .357 average against the Astros for his career is fifth all-time among players with at least 120 plate appearances against the Astros. Hanley Ramirez (.379), Kenny Lofton (.373), Joey Votto (.369) and Bake McBride (.361) are the only hitters with better batting averages against Houston.