SCOTTSDALE, Ariz. -- The Rockies don't need to look externally for pitchers to fill their rotation.

With right-hander Chad Bettis set to undergo chemotherapy for testicular cancer and left-hander Chris Rusin about a week away from throwing because of a right oblique injury, two rotation spots have opened. And while there is plenty of time before the regular season opens for conditions to change, the Rockies' immediate reaction is to stick with pitchers who are big on talent and low on experience.

Right-handers Jon Gray and Tyler Chatwood and lefty Tyler Anderson are expected to start the regular season in the rotation.

Jeff Hoffman and Kyle Freeland were first-round Draft picks and are the club's No. 2 and No. 7 prospects, according to MLBPipeline.com, respectively. Antonio Senzatela , No. 9, has impressed this spring, registering scoreless outings in two of his last three spring appearances. German Marquez is the club's No. 4 prospect, and the Rockies thought enough of him to give up Corey Dickerson for him, acquiring Jake McGee, as well, in a trade with the Rays. Harrison Musgrave , the club's No. 28 prospect, doesn't have the eye-popping velocity some of the others do, but he ascended to Triple-A Albuquerque in 2016.

Chatwood has 90 career games and 89 starts, which are 23 games and 19 starts more than the combined possible starters.

According to scouts from multiple teams and other sources with knowledge of the club, immediate word is the Rockies lean toward staying with pitchers within their system.

Pitching coach Steve Foster understands the Rockies will always scout other clubs. But he's not looking over his shoulder for reinforcements. He's not giving big pep talks, either.

"When they know that you believe in them and you're giving them opportunity, that weighs on the mind of that young player," Foster said.

But the challenge is to earn a spot. Now pitchers are starting to throw four innings or 60-70 pitches, whichever comes first, meaning it's time to earn Major League spots. All the pitchers have had their ups and downs during the spring, but now is the time to show what they can bring to the table in the regular season.

"These next three weeks will be performance-based and critically evaluated," Rockies manager Bud Black said.

Black noted that the some of the better National League rotations have experience. The Dodgers and Giants, who have dominated the National League West recently, fit the profile. But he mentioned the Mets, who made the 2015 World Series, among teams that have won with young rotations.

"It doesn't mean you can't do it with lesser service-time guys, but they have to pitch well," Black said. "Experience tells us there will be ups and downs. You hope the ups hang around longer and the downs are minimal."

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