Manning has played with a slew of receivers over the years, but he hasn't quite seen the combination of size and speed the 6-foot-3, 229-pound Thomas brings to the table.
"He's the biggest receiver I've played with since I've been in pro ball, certainly," Manning said. "Demaryius is a guy who we're going to feature his size and strength and speed. (It) allows you to do certain things with him that other players just can't do."
Manning has also been impressed with the work ethic and playmaking ability of Eric Decker, but it's clear that he is excited about watching Thomas develop into more than a deep-ball threat.
"Demaryius these past two days, he's done some good things with the ball after the catch, which is what we're going to need," Manning said. "You can't just throw down the field every time, you've got to take a five-yard hitch or a 10-yard hook route and turn it into a 20- or a 30-yard gain, and he's shown those type of plays these past two days, and it's a real credit to him."
Thomas played in just 10 games as a rookie due to foot problems, and only 11 regular-season games last year due to a broken finger. However, he averaged 17.2 yards per catch in 2011, and put an exclamation point on his season by catching the game-winner against Pittsburgh in the playoffs.
However, that was in an offense built to suit Tim Tebow, and Thomas was able to burn defenses over-playing the run.
"I think he's come light years in that time from midseason last year all the way through this offseason as well as into training camp," Broncos coach John Fox said.
While Thomas is working on improving his route-running, he also needs to get on the same page as Manning, who is working with a new playbook and a new group of personnel for the first time in his career.
"We're getting better as an offense every day," coordinator Mike McCoy said. "That's the key is everyone gets on the same page and that's something that's going to take time.
"The more we can practice in live situations in pads, the better they're going to get. And that's the entire offense though, not just one guy."
Defensive coordinator Jack Del Rio doesn't have to be convinced about what Manning can bring to the table. He watched the quarterback pick apart his Jaguars defense for years, and now he gets to watch Manning work against his unit every day in practice.
"I'm happy he's on my side now," Del Rio said. "He's got tremendous command of everything he's doing with the offense. He's very demanding of guys around him, which is awesome.
"It's really excellent work for our defense to be stressed every day with a premiere quarterback approaching his job the way he does. It stresses us every day to be better and to be at our best and if we're not, he makes you pay. From that part, I guess I'd say I appreciate that I'm on his side."
-- The Sports Xchange