Street has been hampered by inflammation in his pitching shoulder and has yet to throw in an exhibition game, putting him behind schedule. He threw about 25 pitches Monday and said afterward that his arm "felt great" but had discomfort during his throwing session the next day.
The 26-year-old Street was scheduled for an MRI on Wednesday and Rockies manager Jim Tracy said more information would be known once the results come back.
However, Tracy indicated that having Street ready in time for the opener April 5 in Milwaukee might be a stretch.
"Is it fairly safe to say there's probably a great chance he's not going to be available to begin the season in Milwaukee? Yeah, it's more than likely the case," Tracy said. "We're going to have to adjust accordingly."
Street signed a $22.5 million, three-year deal in January after saving 35 of 37 games for the Rockies last season. He had a forgettable NL division series against Philadelphia, though, losing two straight games.
Over the offseason, Street began his throwing program a little early so he would come into camp in top form.
Instead, his arm has been tight. He shut down his pitching session early Tuesday due to tightness.
"We don't want to push him through it," Rockies head athletic trainer Keith Dugger said. "We're just being safe, being smart right now."
The Rockies' bullpen has been besieged by injuries this spring. Lefty Jimmy Gobble recently hurt his groin, while set-up man Rafael Betancourt has been bothered by an inflamed shoulder. Betancourt threw 25 pitches in batting practice Wednesday and said he liked the way everything went.
"That's what I was looking for," Betancourt said. "Today was the best. I was able to throw all my pitches."
Even if Betancourt is healthy in time for the opener, Tracy wouldn't anticipate using him in the closer's role should Street still be sidelined.
Tracy would rather keep Betancourt as an eighth-inning specialist, a role he filled superbly last season. He was 3-1 with a 1.78 ERA after being acquired from Cleveland in late July.
"This man has been signed up here to be a set-up man," Tracy said. "He is unbelievable with that."
Franklin Morales and Manny Corpas would be the likely candidates to step in for Street, should his arm not be ready. Morales filled in last season when Street missed the final month with soreness in his biceps tendon. The 24-year-old Morales earned a save in six straight outings.
"I try to do my job in any situation," Morales said. "For me to close or whatever, if you give me one inning as a reliever, that's OK for me."
Corpas was the Rockies' closer in 2007, helping the Rockies to the World Series that season. He was beaten out by Street last spring, only to win it back in April. Soon after, Street took it back.
"I'm glad today is only St. Patrick's Day. We've got some time," Tracy said. "There's a lot of different options as to how this all plays out."
Todd Helton, Colorado Rockies agree to two-year extensionMathieu’s season appears over
