ST. LOUIS --Within the first 32 minutes against the Rams, three of the Broncos' key offensive weapons exited with injuries that would keep them out of the remainder of the game.

But Peyton Manning said after the game that the attrition on that side of the ball doesn't justify what ended up being the lowest scoring performance by the Broncos' offense since Manning arrived in Denver.

"No excuses," he said. "I have to play better and we've got to score more points than seven."

Montee Ball, who had missed the last five games with a groin injury, played just a few snaps before aggravating the injury and not returning. Julius Thomas hurt his ankle on the Broncos' first possession and remained out. Then, on Denver's first possession of the second half, Emmanuel Sanders suffered a concussion on a big hit from Rams safety T.J. McDonald.

The absence of Thomas and Sanders took away weapons that have accounted for 19 of Manning's 30 touchdown passes this year, including a 42-yarder that Sanders caught in the second quarter for the Broncos' only points of the game. Virgil Green missed the game because of a calf injury and rookies Cody Latimer and Kapri Bibbs were both inactive as well, leaving the Broncos with two running backs, four receivers and one tight end available by game's end.

But even with Andre Caldwell and Jacob Tamme stepping into bigger roles, Manning expected much better from the offense.

"Certainly that's been the motto of this team and this offense is that when somebody goes down, somebody is there to step in," he said. "And I have all the confidence in the world in both Bubba and Jacob and I have to give them a chance to make plays.

"You hate to see Julius and Emmanuel injured, but like I said I don't think that's an excuse."

Manning noted that his "heart drops" when one of his receivers gets hit like Sanders did, who took a shot up high from McDonald that drew a 15-yard penalty for unnecessary roughness on a deep ball down the right sideline.

"I feel a part of that," Manning said. "I felt like I probably could have held the safety a little bit longer, keep him from getting a jump on that. Every pass I throw, you feel responsible for it, especially if he gets injured, so I hope he's okay.

"And for whatever reason, right after that play, I think we went three incompletions and weren't able to get that drive. So that was a disappointing drive to start the second half and we came away with no points and no points the entire second half."

Sanders' injury came at a key moment: The Broncos had cut the Rams' lead to six points late in the first half and Head Coach John Fox had considered using his timeouts to get the ball back before halftime, but knew Denver would start the second half with the ball. "He just said, 'We've got the ball first in the second half, let's go do it,'" Manning said of Fox.

The Broncos had moved the ball a bit before Sanders' injury and were at the Rams' 38 after the penalty, but couldn't pick up any more yardage and punted from the 43 after a false start penalty. The drive was representative of many of the Broncos' drives on the day, as they moved the ball across midfield but were unable to reach the red zone or reliable field goal range.

Manning and Co. picked up at least 22 yards on 10-of-11 meaningful possessions (excluding series that started within the final 25 seconds of each half) and at least 30 yards on six of those possessions. Both their total yards (397) and yards per play (6.0) on the day exceeded the Rams' output (337 and 5.2 respectively), but the Broncos' couldn't convert in key moments. With their only score coming from the 42-yard line, the Broncos didn't reach the red zone once on Sunday despite moving the ball effectively at times.

"That's probably what makes it even more disappointing, because it's one thing if you're just three-and-out from the 20 every time, but we did have good starts to drives," Manning said. "...I feel like I didn't do my job well enough to get us past that to get us down in [the red zone]. We had a good red-zone plan, and I don't think we ever got to call any red-zone plays.

"When your defense is holding them to just field goals and you have the chance to score points, that's on us. We've got to do a better job scoring points."

The Rams' pass rush, which had picked up 16 sacks in its last four games, bothered Manning throughout the day. It didn't help that Manning was forced to throw 54 times with the Broncos trailing, the second time in three weeks that he's had at least that many attempts, after he had 57 against the Patriots in Week 9.

As John Fox put it, "Whenever you get one-dimensional, they're teeing off on you. It's not a fun day at the office if you're playing up front."

"That's probably not the ideal scenario that you want to take place coming into the game, so I think that plays into [the Rams'] strengths a little bit," Manning added. "But those are passes I've got to complete and I thought the guys up front fought like crazy against a good rush.

"I didn't feel like I carried my weight today and offensively we've got to score more points than seven. That's pretty plain and simple. ...Certainly we have to take responsibility for not doing our job on offense, and that starts with me."

Manning and Co. will have an opportunity to bounce back next week against the Dolphins, Denver's first home game since October 23, a Thursday night win over the Chargers.