ENGLEWOOD, Colo. — Shortly after rookie quarterback Drew Lock jogged off the field following his first practice with the Broncos, he admitted he had a lot to learn.

During that May 10 practice, Lock realized calling plays in the huddle and operating under center would be no easy task.

And speaking to the media, he vowed he would improve.

Nearly three weeks of practice later, Lock said he's taken the next step in his development.

"Compar[ing] Day 1 to now, I'd say [my comfort level is] 1,000 times better," Lock said Wednesday at the Broncos' first annual Round with the Rookies presented by Coca-Cola. "It took some extra grind, some extra work where you think you know what it takes and then you realize quickly that you're going to have to put a little bit more into it.

"Once I think I figured that out, it became a little more smooth for me."

Lock's first few weeks of organized team activities haven't been mistake-free, but he said he and Offensive Coordinator Rich Scangarello have focused on correcting issues and moving forward.

"He's definitely been OK with me making the mistake — but definitely not making the mistake twice," Lock said. "I think that's been the one thing we've focused on. We knew I was going to come in, I was going to have to learn how to operate from under center, how to call plays in the huddle, learn a pro-style offense. It's all new to me. So I think with how he's treated me is 'You can make a mistake, but let's come back and let's fix it.' I think that's been the biggest thing for us."

Lock said he's made a list of his mistakes each day and focused on improving in those aspects during the following practice. The goal, the second-round pick said, is to make that sheet of mistakes a little bit smaller each day.

Joe Flacco, the team's starting quarterback, has done his share to help Lock as the rookie learns a new system.

"Joe's been awesome," Lock said. "It's hard not to talk to a guy when you're in the same quarterback room and you're this close to each other on the practice field to where if I do have a question and I ask him, he's very willing to talk to me about it. So I'm very appreciative for what he's done for me up to this point."

As Lock works toward a higher level of performance, he said he won't let inevitable interceptions or bad practices weigh on him.

"I think as a Q [quarterback], you've definitely had that practice throughout the years," Lock said. "You throw a couple picks, figure it out, how to come back from it. You might be struggling with a pick early in your career and then when you throw a pick later in your career, you figure it out. I think I've figured it out."

Lock said he's also discovered a critical lesson that can only help him as he competes for the team's backup quarterback role — and for a starting job later in his career.