DENVER -- After feeling pain in his throwing elbow late in his start Sunday in Toronto, Rockies left-handed starter Kyle Freeland landed on the 15-day injured list on Friday with a left elbow strain.

Freeland has a 13.21 ERA in 15 2/3 innings over four starts this season. He struggled mightily in his first two outings, but has pitched better in his last two, both covering five innings -- a no-decision at home against the Diamondbacks on April 8 and Sunday’s loss at Toronto.

However, there were warning signs after the first solid effort, although he didn’t believe they were severe enough for concern. He felt discomfort late in Sunday’s start, and his arm didn’t bounce back in succeeding days. The expectation is he will need rest and eventually a Minor League rehab stint -- a period manager Bud Black estimates at “a month to six weeks.”

But Freeland -- in the third year of a five-year, $64.5 million guaranteed deal -- and Black said they are confident the injury is not to his ulnar collateral ligament, a condition that usually portends surgery.

“We had imaging yesterday, and it’s an elbow strain,” said Freeland, who said he plans to study the results further with the Rockies’ medical director, Dr. Thomas J. Noonan. “We’re taking the steps moving forward to make sure we’re as cautious as possible, so we don't further damage it or rush me back too quickly.

“Obviously, when it comes down to elbows, there's going to be concern with the UCL," Freeland added, "so that's why we're taking it very cautiously moving forward.”

Freeland struggled last season, finishing with a 6-14 record and 5.03 ERA in 29 starts, and dealt with a vexing dip in velocity during the middle months. By giving greater attention to arm care, especially in his shoulder, Freeland saw improvement toward season’s end and concentrated on arm strength through the winter. He had a solid spring before struggling early in the regular season, but pitched with velocity reminiscent of a few years back.

“I dipped into a couple of different kinds of programs on my own, some stuff that I've spoken about with our trainers, with our strength coaches and with people that I work with outside of our clubhouse staff, to strengthen my arm and get it to where I want it to be,” Freeland said. “And we got it there. I do not know if that's any correlation to my injury. I really hope not, because I enjoy that work process.”

Black added, “Hopefully, it’s just a little strain, trauma from throwing a baseball.”

In Monday night’s game at Philadelphia, the Rockies had a depleted bench and needed to use Freeland as a pinch-runner in the ninth inning. He unsuccessfully tried to score when a pitch eluded the Phillies’ J.T. Realmuto, and sustained a slight right shoulder separation in a collision at the plate with pitcher Jeff Hoffman.

Freeland, who had a similar injury to his non-throwing shoulder last season and said the shoulder popped immediately into place on Monday, said the left elbow injury was totally unrelated to the collision with Hoffman.

Freeland also said he doesn’t think a grip change on his changeup, adopted late last season, led to pain. But he, as many pitchers have during the early-season spate of elbow injuries, theorized that a change in the pitch timer -- from 20 seconds to 18 with any runner on base, but still at 15 with bases empty -- may be a factor.

“I'm a firm believer that there is something that correlates with pitch clock and pitchers,” he said. “We're exerting our bodies at 100 percent every 15-18 seconds. You do that, it’s tough. You do that in Colorado, even tougher.”

Injuries to Freeland’s throwing arm have been limited in his time with the Rockies. Since debuting in 2017, Freeland has logged 1,000 innings, bested by only 14 pitchers during that time. The lefty has cleared at least 100 innings in every season outside of the COVID-shortened 2020 campaign.

Black said the Rockies will move long reliever Peter Lambert (2-0, 2.31 ERA in six appearances) to the starting rotation to start Sunday’s nightcap of a doubleheader against the Mariners. Friday’s game was postponed because of a wintry mix that hit the Denver area.

The Rockies also recalled right-hander Noah Davis from Triple-A Albuquerque to replace Freeland on the active roster. Davis will assume Lambert’s long relief role.