Fangio told reporters, "He's a hard-throwing pitcher who doesn't know how to pitch yet."
Lock, a second-round pick out of Missouri, is expected to serve as the Broncos' backup quarterback in 2019 after they acquired veteran Joe Flacco from the Baltimore Ravens in March.
The Broncos and Lock finally came to terms on a rookie contract this week, which allowed him to participate in the team's first day of training camp Thursday.
Lock told reporters he wanted to ensure he didn't miss any valuable practice time:
"I was anxious to get out on the field. I knew from my side of the party, we were trying to get things worked out. The Broncos and my agency were working together, but I told my agency beforehand that if it got to the point where I was missing practice, then there was no chance we were going to go on with it. I was going to sign a deal and I was going to get here, because the most important thing to me was getting out here."
With Lock signed, Fangio discussed his expectations for the rookie signal-caller during training camp: "Command of the offense. Command at the line of scrimmage. Decisions on where to throw the ball, how quickly he can make those decisions. Just become a quarterback."
While Lock is just beginning his NFL career, he showed off his elite arm talent on multiple occasions during his first training camp practice:
Lock put up big numbers during his collegiate career at Mizzou despite playing in the SEC, which features many of the best defenses in the nation.
After completing 57.8 percent of his passes for 3,964 yards, 44 touchdowns and 13 interceptions in 2017, Lock completed 62.9 percent of his attempts for 3,498 yards, 28 touchdowns and eight picks last season, along with six rushing scores.
Denver opted against taking a quarterback in the first round of the 2019 NFL draft, but when Lock dropped into the second round, the Broncos traded up 10 spots from No. 52 to 42 to draft him.
Until Lock is ready to step in as the starter, he will learn behind a Super Bowl MVP-winning quarterback in Flacco.