SCOTTSDALE, Ariz. -- Peter Lambert has passed enough tests this spring to earn a slightly bigger test -- a start in Friday’s Cactus League game against the Royals at Salt River Fields at Talking Stick.

Displaying an advanced fastball-changeup combination, the 21-year-old Lambert, who is ranked the Rockies' No. 4 prospect by MLB Pipeline, has posted a 4.66 ERA in his first four Cactus League appearances, spanning 9 2/3 innings. But in his last outing, the right-hander threw 3 2/3 innings, allowing one run on one hit and one walk during the Rockies’ 5-1 victory over the D-backs in Monterrey, Mexico, on Saturday.

“It’s a mixture of the things he’s done and the things that we believe he can do,” Rockies pitching coach Steve Foster said. “This guy has a calmness about him, a maturity beyond his years. All that being said, that’s a formula for opportunity.”

The Rockies' starting rotation is difficult to crack. Righties Jeff Hoffman and Antonio Senzatela appear on the outside looking in, despite having Major League experience and having thrived this spring. But Colorado's decision to move lefty Tyler Anderson to a Minor League game and put Lambert on the mound on the big field suggests Lambert is beeping loudly on the club's radar. The Rockies gave him a taste of Major League Spring Training early last year before sending him down. This year, the Rockies have made their first cuts, and Lambert, who finished last season at Triple-A Albuquerque, has done enough for manager Bud Black to offer him a bigger bite.

“Based off of last year, I thought I’d be coming mostly out of the bullpen [during spring], but I’m just super excited for the opportunity,” said Lambert, a second-round Draft pick out of San Dimas (Calif.) High School in 2015.

Lambert, who turns 22 on April 18, blew through Double-A last year, notching a 2.23 ERA across 15 starts. He had a 5.04 ERA in 11 starts at Triple-A, and that stint showed what he must improve. Lambert's fastball command was not as effective at the highest Minor League level.

“Coming into camp, I wanted to work hard on my fastball command, dialing that back in, and work on the glove-side fastball as much as I can,” Lambert said. “It’s getting a lot better. I still need to work on it, though. That’s my plan the rest of spring.

“I’m a pitcher, and I need to evaluate each and every pitch that I throw. That’s what I do after my starts.”

The clean-shaven Lambert lacks the grizzled look of a big leaguer, but no one is checking and questioning his ID.

“I don’t care what he looks like as long as he keeps the fastball down, locates it in on the hands, changes speeds, bounces the curve when he needs to, lands the curve -- when he’s behind in the count -- for a strike,” Black said. “That’s what I care about.”

However, some attention is paid to his interaction with teammates. If he were intimidated or in awe of the atmosphere, or if he let his surroundings interfere with work, it would at least give the Rockies pause. As Black has said, merely being in big league camp meant you’re on the radar, and Triple-A is a phone call away.

“He’s got on-the-field seriousness, clubhouse playfulness,” Foster said. “That’s a great combination.”