For a quarterback who hasn’t been in Denver all that long, Peyton Manning sure has gone through his share of starting running backs.

Willis McGahee. Knowshon Moreno. Montee Ball. Ronnie Hillman.

Wait a minute. Ronnie Hillman?

“Ronnie has played at different times, in different amounts, but when you’re the starting back and running out there in pregame warm-ups as a starting back, it’s a different hat that you wear,” said Manning, who is but a quarter of the way through his third season in Denver. “There’s no question he has a burst that is pretty unique when he gets the ball in his hands. It’s our job to give him space.”

Hillman has taken a while to get his career going since he was a third-round pick in the 2012 draft, but he has come a long way since he was deactivated from the Broncos’ Super Bowl loss Feb. 2 at New Jersey’s MetLife Stadium.

That same venue will mark Hillman’s first NFL start Sunday against the New York Jets.

“Any competitive person, their patience will be tested when they’re not playing as much as they want to,” Hillman said Wednesday before a media throng in front of his locker.

He is starting partly because Ball went down with a groin injury Sunday against Arizona. But Hillman also earned his start through a strong second-half performance. Through halftime of the Broncos’ fourth game, Hillman had 1 yard rushing on three carries. He was plenty busy in the second half of Game 4 on Sunday, though, with 14 carries for 65 yards.

He needed that game. For many reasons, Hillman has been slow to develop into the kind of change-of-pace back the Broncos envisioned when they drafted him out of San Diego State, where he averaged 1,622 yards per season as a freshman and a sophomore.

“He’s chronologically young,” Broncos coach John Fox said of Hillman, 23. “He’s probably one of the younger players still. And offensively we’re not the easiest system. There’s so much more to it than running the ball. Playing receiver is so much more than just good hands. Playing quarterback is about so much more than a strong arm. He’s learning.”

Hillman didn’t play as a rookie because he was a rookie. But after running for a career-best 83 yards in the Broncos’ frigid playoff game against Baltimore, he was expected to start in his second season of 2013.

It didn’t happen. A fumble at the goal line in a preseason game at Seattle followed by Moreno’s career year again left Hillman on the sideline — often in street clothes.

Hillman was supposed to open this season as Ball’s backup, but he fell ill after the Broncos’ final preseason game in Dallas and didn’t get his first carry until the Broncos’ third game at Seattle. Finally, in the Broncos’ 41st game (counting playoffs) since he was drafted, Hillman will be Manning’s starting running back.

“You feel a little more responsibility to go out there and perform right away, not watching somebody else go out there,” Hillman said.

Initially, the Broncos thought Ball was headed for injured reserve with a designation to return after eight games. That’s why the team brought in veteran running backs Mikel Leshoure and LaRod Stephens-Howling for workouts Tuesday.

But a magnetic resonance imaging exam offered hope Ball might miss only a month or so with his groin strain. The Broncos added running back depth Wednesday by signing former Oakland Raider Jeremy Stewart to their practice squad, but otherwise the team is planning on going with Hillman, C.J. Anderson and Juwan Thompson until further notice. Thompson, a rookie, sat out practice Wednesday with a sore left knee.

“You can’t do it with just one back in today’s game, so we expect C.J. to do his job, Juwan to be ready,” Manning said. “Those guys are both young backs, but both act like older players. I think we’ll need the whole committee against these guys, and we’re trying to get that running game going.”

Mike Klis: mklis@denverpost.com or twitter.com/mikeklis