ENGLEWOOD — It’s almost automatic when rookie cornerback Isaac Yiadom enters the game.

Here comes a pass to the receiver he’s covering.

Yiadom will start in place of the injured Chris Harris Jr. today against the San Francisco 49ers at Levi’s Stadium so don’t be surprised if quarterback Nick Mullens looks his way as Yiadom covers the likes of Marquise Goodwin or Dante Pettis.

“I expect that," Yiadom said in a sit-down interview with 9News this week. “I like it. Every time I go in the game, like, against the Steelers, I told my safety, ‘They’re coming right at me so let’s make it happen.’

“I like it. It’s boring playing corner if nobody comes at you. You’ve got to get some stats, got to make some plays. … I’m definitely trying to prove myself to let quarterbacks know they’re going to pay if they throw the ball my way. So, I’m going to try and get better every single day. I expect them to throw the ball my way and make them pay for it."

Had Harris gone down earlier this season, the Broncos would have been trouble. Yiadom opened eyes during the offseason and training-camp practices, to the point he got an unexpected quick promotion to No. 3 cornerback behind Harris and Bradley Roby. But then came the preseason schedule and Yiadom looked like the rookie he was.

He struggled to the point the Broncos decided to sign 35-year-old corner Adam Jones, who went all spring and summer without a team, just two weeks prior to the start of the regular season.

“Yeah, I let up a little slant on Stephon Diggs, I remember that," Yiadom said of the Vikings’ star receiver in the first preseason game. “And then a 7-cut (deep sideline route) against the Bears (Kevin White, who drew a 37-yard pass interference penalty). I mean, those are good receivers. Got to go against them. That’s my job now, I’ve got to cover them, so it doesn’t matter how good they are or if I have a safety over the top or what. I’ve got to do my job.

“I don’t know maybe just my first couple NFL games I had a little jitters, something like that, but now I’m super comfortable back there. I feel like my safeties can trust me, I can trust them. The secondary knows I’m coming out to compete so now I’m not stressing. In the beginning, learning experience, you’ve got to make mistakes to learn."

After four years at Boston College, finishing with a degree in communications, Yiadom was drafted in the third round by the Broncos, primarily because he impressed them while playing for the Broncos’ coaching staff during Senior Bowl week.

“I loved the way they coached me at the Senior Bowl," Yiadom said. “They coached me so hard and made sure I was going after the ball every single play.

“Went out there had a great day and let them know that when they drafted me, they expected a lot out of me. I try to come out here and give them 100 percent every time. Every time I go out on the field, in the game, I try to give 100 percent, compete, let them know that I was worth the draft pick where they chose me at. I love the coaching staff. I will keep playing hard for them."

Yiadom is an extra-credit guy. One of the first lessons virtually all rookies must learn is how to work. Not work as they did in college when football was a part-time job. Work as a professional.

Yiadom, though, was born with a work ethic. He was, without exaggeration, the first player on the field for the start of training camp every day. Stepping through the ladders. Working on his footwork.

“In my coaching career I’ve coached a lot of young corners," said Broncos’ defensive coordinator Joe Woods. “He is a guy that is going to do it exactly the way you tell him. At some point he has to release that a little bit and just go play football. I think the more he plays, the better he’ll get. I look forward to him playing this weekend."

An earnest kid who strives to be great, or at least the best he can be, Yiadom has improved immeasurably as this season goes along – enough for the Broncos to release Jones. Yiadom bit on a sideline-and-go on his first play against the Steelers two weeks ago. But once he got a lucky overthrow by Ben Roethlisberger, Yiadom settled in and played well.

“I remember ‘14’ (rookie receiver Courtland Sutton) catching the ball and I remember ‘41’ (Yiadom) defending him, every single time," said star pass rusher Von Miller. “His growth has been right there with Courtland’s and we all see what Courtland has done on the field.

“Isaac is ready to go. He’s been in and out of the game in spurts. He’s been doing a great job here in practice, and I’m excited for him. He was a big-time corner in college, and he’ll be a big-time corner in the league."

Thing is, the Broncos need Yiadom to become a big-time corner today. With not only Harris out with a fractured fibula but veteran cornerback Tramaine Brock down with a rib injury, Yiadom is in the spotlight of his first NFL start Sunday in a game the Broncos must win to stay in the playoff race.

“I’m ready. Been ready," Yiadom said. “We’ve got a bunch of great corners on this team. It’s unfortunate what happened to Chris, but all season I was staying prepared every week because you never know what’s going to happen. Maybe a player needs a break for one play or somebody goes down, I’m going to have to be the next-man up. So, I’ve been preparing like I’m the starter. Now it’s here so I’ve got to make the most out of it."

Said head coach Vance Joseph on his starting rookie corner: “He’s playing with more confidence. Obviously, being a young corner in this league is a tough duty. They’re throwing the ball all over the place and every play can be a touchdown if you’re not focused. He understands that. He is a very, very focused young man. He’s tough, he likes to play, he likes to practice, he’s long and he has a short memory. If he makes a bad play, he forgets about it. He’s that competitive. The more he plays, the better he will get."