DENVER (AP) -- Not so long ago, Rockies manager Clint Hurdle wondered how much longer he could keep sending Ubaldo Jimenez out to the mound.
"He wasn't giving us innings," Hurdle said. "He wasn't giving us consistency and we weren't sure we were helping his development."
Things sure have changed.
Jimenez will try to win his fifth straight in the second game of a doubleheader between the Rockies and Washington Nationals on Thursday. The 24-year-old Jimenez started the season 2-8, but is 6-1 since then and hasn't allowed a run in 13 straight innings.
"I knew I was doing bad, but I never stopped believing that I had major league stuff and could give my team a chance to win," Jimenez said. "It was a matter of putting it together."
The scheduled game between the Nationals and Rockies on Wednesday night was rained out, prompting the Thursday doubleheader beginning at 3:05 p.m. EDT.
The Nationals planned to place outfielder Elijah Dukes on the 15-day disabled list Thursday, retroactive to Aug. 3, because of a right calf strain.
Dukes, who has already been on the DL twice because of right hamstring and knee problems, was batting .264 with six homers and 23 RBIs in 54 games.
General manager Jim Bowden said the club would recall right-hander Garrett Mock from Triple-A Columbus, where he was 6-3 with a 3.01 ERA in 19 games. In five appearances this season for Washington, Mock allowed eight earned runs in 13 2-3 innings.
Jimenez started to turn things around when he threw seven scoreless innings in a 1-0 win over San Francisco on June 11. Ten days later he got his first win in more than two months when he outpitched fellow Dominican star Pedro Martinez in a 7-1 victory over the New York Mets.
After losing to Detroit 7-1 on June 27, Jimenez has been dominant. He was 5-1 with a 1.74 ERA in July, including a 10-1 win over the Los Angeles Dodgers on July 22 in which he threw his first complete game.
Since his loss in Detroit, Jimenez has lowered his ERA from 4.71 to 3.61 and has pitched into the seventh inning in five of his seven starts.
"We're seeing him grow," Hurdle said. "He's making positive strides. Every time out we're seeing something a little bit different."
Francis was activated from the disabled list Wednesday and will make his first start since June 28 against Detroit.
He was 17-9 last season and emerged as the team's ace, but struggled to a 3-7 record and 5.67 ERA this year. He went on the DL with left shoulder inflammation on June 29, and said he doesn't feel any pain after three rehab starts.
"He feels healthy, he feels prepared, everything that Jeff always brings to the table," Rockies pitching coach Bob Apodaca said. "He was looking forward to today, now it's just delayed."
Apodaca was happy Wednesday's game was called before Francis started warming up.
"You never want a starting pitcher on either side to get ready then have to stop," he said.