It’s fast times for Dodgers’ Rubby De La Rosa

Reporting from Denver

Rubby De La Rosa said he knew how hard he had thrown the ball to strike out Troy Tulowitzki to end the third inning.

“Whenever I pitch, I always look,” De La Rosa said of the stadium radar gun.

In this instance, the pitch registered 100 mph, the first triple-digit clocking by a Dodgers pitcher since Jonathan Broxton in 2009.

“That’s normal,” De La Rosa said, smiling.

A stand-in for the sidelined Jon Garland, De La Rosa improved to 3-0 in the Dodgers’ 10-8 victory over the Colorado Rockies on Sunday.

But the rookie right-hander’s day was cut short by a forearm cramp.

“When I bent my finger, I couldn’t open it back up,” he said.

So, one pitch into the sixth inning, De La Rosa had to be replaced by Ramon Troncoso. De La Rosa was charged with three runs, three hits and three walks in five innings. He struck out six.

All three runs the Rockies scored against De La Rosa came in the first inning, when he gave up a leadoff double to Carlos Gonzalez, walked Tulowitzki and served up a towering home run to Seth Smith.

“He didn’t seem fazed by it,” Manager Don Mattingly said of Smith’s blast. “He kept pitching. He started using his changed and breaking balls more.”

In the process, De La Rosa learned a valuable lesson: to drink more water. He said he was told by the team’s medical staff that the forearm cramp was likely a result of dehydration.

Mattingly said he expects De La Rosa to be able to take his next turn in the rotation.

Like old times

James Loney hit a third-inning grand slam that gave the Dodgers their first lead of the game, 4-3.

Loney’s only other career grand slam was also hit at Coors Field, on Sept. 28, 2006, the day he tied a franchise record by driving in nine runs.

In 43 games at Coors Field, Loney has hit eight home runs and driven in 49 runs.

“I don’t know what it is,” he said.

Gwynn’s glove

Left fielder Tony Gwynn Jr. made a game-ending diving catch with the bases loaded to preserve the Dodgers’ 11-7 win over Colorado on Saturday night.

The catch was the second game-saving diving catch Gwynn has made to end a game. He sealed the Dodgers’ 3-2 victory over the San Diego Padres on April 29 with a similar grab.

On Saturday, Gwynn said he had a special source of motivation: a trash-talking fan.

After Young lined into the double play in the ninth inning, Gwynn said he taunted the fan who had berated him the entire game.

“I put my glove on my back side and acted as if was a mouth,” he said.

But …

“Never fails,” Gwynn said. “Every time I start popping off, the other team rallies. I was thinking to myself, ‘Oh God, what did I do?’ ”

So Gwynn said that when he caught the ball, he couldn’t wait to get up and search the stands for the loud-mouthed fan.

“I just winked at him,” Gwynn said.

dylan.hernandez@latimes.com