Decker has been the star of the Broncos' training camp so far, but when he went out with a strained groin, Demaryius Thomas stepped up to solidify his standing in Manning's eyes and with Denver's refurbished offense.
Thomas made several big catches Thursday, even turning a rare wobbly pass from Manning into a 35-yard TD when he outleapt Drayton Florence and Rahim Moore at the goal line. Another time, he gave Tracy Porter a taste of the stiff-arm he used on Ike Taylor to beat Pittsburgh in the playoffs.
Whether on posts, curls or slants, Thomas was there to haul in Manning's fastballs during the no-huddle work to the delight of yet another record crowd -- 5,034 -- at Dove Valley.
"Well, I think Demaryius has had a really good camp even when Eric's been practicing," Manning said. "Demaryius is a guy that we are going to feature. His size and strength and speed just allows you to do certain things with him that other players just can't do. And so, Eric's had a really good camp. He's just got a little tweak, hopefully he'll be back this afternoon or tomorrow.
"But I thought Demaryius these last two days has really made some big plays, he's done some good things with the ball after the catch, which is what we're going to need."
After all, Manning's game is built on finding the hole in the defense and getting the ball there as quickly as possible so his receiver can use his legs to turn short passes into long plays.
"You can't just throw down the field every time," Manning said. "You've got to be able to take a 5-yard hitch or a little 10-yard hook route and turn it into a 20-yard or a 30-yard gain and he's kind of shown those type of plays these past two days."
Good thing, too, because Thomas had some catching up to do.
The oft-injured Thomas needed an operation to remove pins from his left thumb this offseason and was sidelined when Manning signed with the Broncos in March.
So, he was rehabbing while Manning was throwing tons of passes to Decker at local high school football fields while working his way back from a nerve problem in his neck that caused him to miss all of last season and led to his release by the Indianapolis Colts.
Thomas returned to the field in May and quickly made a big impression on Manning, who never had such a huge target in Indy.
"He's the biggest receiver I've played with since I've been in pro ball, certainly," Manning said. "He has that rare combination of size and speed. So, I look forward just to getting more and more comfortable with him and just kind of growing through this process.
"And every day is important with not just him but all of the receivers as we work together to get on the same page in many different phases."
Also making plays and an early impression on Manning is free agent receiver Andre "Bubba" Caldwell, who signed with the Broncos this offseason after four years in Cincinnati.
"Bubba Caldwell has excellent speed, has a rare speed to really get deep," Manning said. "Corners, you can tell when they're covering him they're going to maybe be off a little bit more knowing that if you miss one step he can be right by you. And he's obviously adjusting to a new offense like all of us are. I like working with Bubba. He's a hard worker and really has a lot of explosive plays in him, I think."
After Decker, Thomas and Caldwell, there's Manning's old pal Brandon Stokley, leaving one or two roster spots for the rest of the receivers to fight over.
Nagging injuries have hit the back of that receiving corps with Greg Orton (ankle), D'Andre Goodwin (foot) and Tyler Grisham (knee) joining Decker on the sideline Thursday. The Broncos brought in Cameron Kenney off waivers from Seattle to fill in.
Manning's timing hasn't been crimped by the steady stream of receivers hobbling off the field, however, and he said he's pleased with the progress the offense has made in the first week of training camp.
"That's a process. It starts in the offseason: OTAs, minicamp, training camp and really throughout the preseason. I think you learn a little bit more about each guy every time you throw to him," Manning said. "Obviously, I've thrown a ton of passes throughout my career to both Jacob (Tamme) and Brandon, so it's nothing you can really rush. It takes practices, it takes different scenarios, different types of situations, two-minute, red zone, third down and the more game-like situations, which is what we're doing more of now."
Also helping Manning get up to speed is a stout secondary led by Champ Bailey.
"I've said that all along, it's a great challenge going against our defense. There's a lot of speed out there, a lot of experience," Manning said. "... And so it's a good challenge every day. We're going to win some battles; they're going to win some battles. But it's good. It's making the Broncos better and I know it's really good for our receivers and for our timing."
Defensive coordinator Jack Del Rio doesn't relish facing Manning every day in practice, but, hey, it's better than seeing him across the field on Sundays like he did so often while coaching the Jaguars.
"He was a thorn in my side when I was in Jacksonville. I'm happy he's on my side now," Del Rio said. "... He's one of the better quarterbacks to ever play. He's got tremendous command of everything he's doing with the offense and 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."