DENVER -- Paxton Lynch fought off nerves Sunday in his first NFL start as the Denver Broncos' quarterback.

But he couldn't overcome the Atlanta Falcons.

Atlanta sacked Lynch six times as he finished 23-of-35 for 223 yards with a touchdown and an interception in the Broncos' 23-16 loss, their first of the season.

Lynch looked unsettled in the pocket at times against a Falcons defense that entered the game 30th in the league in total defense, 31st in pass defense and with just four sacks.

"Obviously you have some butterflies in your first NFL start," Lynch said. "It's not a preseason game and your team is 4-0. You are excited about that, but you have to focus on the team and winning the ballgame. After that first drive, I was ready to go and ready to play with those guys."

Lynch, the Broncos' first-round draft pick in April, started while Trevor Siemian recovers from a left shoulder injury. Siemian, who had practiced on a limited basis this past week, was ruled out after a brief throwing session Saturday.

Lynch fumbled twice -- the Broncos recovered both -- and before a surge in the fourth quarter, which the Falcons entered leading by 17, he had just 101 yards passing.

"I am upset, obviously, because we lost," Lynch said. "I am kind of happy that I got the first one under my belt. My first start with these guys and having a chance to play with them. If I get put in that situation again, I will know how to handle it a little bit better than I did the first time. I am glad I got the experience, but I am also upset that we didn't come out with the win."

The Broncos also didn't provide Lynch the best of support, rushing for 85 yards in their third consecutive game with less than 100 yards rushing.

The Broncos' pass protection was spotty at times, as well, with right tackle Ty Sambrailo being replaced in the fourth quarter.

"We have to help him better, us as coaches," Broncos coach Gary Kubiak said. "We got down early in the game. We were committed to running the ball [Sunday] and tried to do that early. We did not run the ball well. We get down by 13, something like that, and were struggling to protect him. We put him in a really tough situation. That's not the type of game you want to put him in."

It was uncertain whether Lynch would start the Broncos' Thursday night game at San Diego, which stands as the shortest turnaround between games they face this season.

Siemian said after Sunday's game that he had thrown "a little bit" at the team's practice Saturday when it was determined he would not play against the Falcons. Siemian also said he still believed he was close to returning to the lineup but would see how he felt this week and what the team's medical staff said in the coming days.

"We'll see. ... I'll take it one day at a time and get right [Monday]," Siemian said.

Said Lynch: "I'm just going to keep approaching it like I have been approaching it. I am going to take it day by day, and if my number gets called again, then I am going to make sure I am ready to go out there and play. If my number isn't called, I am going to make sure to be ready to play if I have to go back in the game again."