Apparently, when the Denver Broncos kick out reporters and close the doors for the bulk of their practices during the week, they don’t have their backup guys stand around or fetch water for the starters.

They get their reserves ready to play.

Paxton Lynch, a first-round quarterback from Memphis, didn’t play a snap in the Broncos’ first three games as he watched the pleasantly surprise ascension of second-year quarterback Trevor Siemian.

When Siemian went down with a left shoulder injury in the first half of the Broncos’ fourth game here Sunday against the Tampa Bay Buccaneers, Lynch was thrown into the game.

And he kept on throwing while helping the Broncos defeat the Bucs, 27-7 in a game that was delayed 1 hour, 26 minutes midway through the fourth quarter because of a storm.

"Like I said from the beginning, my thing is prepare like you're going to play every game,'' Lynch said. "When Trevor came out with the injury I was prepared to go in. Obviously, I was nervous just because it was my first time going in, but I was definitely prepared, ready to play.''

The Broncos are now the NFL’s only 4-0 team. Philadelphia, which is on its bye week, and Minnesota, which plays Monday night, are both 3-0.

Lynch wasn’t exactly coddled in his NFL debut. He completed 14 of 24 passes for 170 yards in leading three, lengthy scoring drives. Those 24 pass attempts came from 2-minute warning in the first half until he threw his first career touchdown pass to Emmanuel Sanders with 9:01 left in the fourth quarter. The first two drives ended in Brandon McManus field goals. The third ended with a well-executed, play-action rollout and easy flip to Sanders from 5 yards out.

Sanders performed a cartwheel in the end zone to celebrate his touchdown.

"A perfect 10,'' Sanders said in what was clearly a biased assessment of his field exercise.

Siemian was the AFC Offensive Player of the Week following the Broncos win at Cincinnati last Sunday when he threw for 312 yards, four touchdown passes and no interceptions in winning his first-ever road game.

His second road challenge didn't go as he hoped. With 3:25 left in the second quarter, and his team up 14-7, his left shoulder was slammed onto the Raymond James Stadium grass field as he was getting sacked -- and rather viciously tossed around -- by Clinton McDonald. Siemian stayed in to hand the ball off to running back Devontae Booker, who gained 11 and took the clock to the 2 minute warning.

At that point, Siemian was taken out and carted into the locker room.

"I ran another play and I figured something was up,'' Siemian said. "I went over to Greek (Broncos trainer Steve Antonopulos) and he said, probably take five, at least.''

Siemian will undergo further tests and evaluation Monday. The initial finding was Siemian has a sprained AC joint in his left, non-throwing shoulder simiilar to the injury New England quarterback Jimmy Garappolo suffered to his right throwing shoulder two weeks ago, sources told 9News. Garappolo missed the past two games with his injury, but again that was to his throwing shoulder.

Siemian's injury was to his left shoulder.

"I can tell you we felt like we could have put him back in the game,'' said Broncos head coach Gary Kubiak.

Siemian was dressed in uniform on the sideline in the second half and was available to play in an emergency. But now that the Broncos got through this game, the expectation is veteran Austin Davis will be the backup to Lynch for the next week or two.

"That's my expectation coming in here, to learn the playbook as fast as possible and be ready to roll when and if I'm called upon,'' Davis said.

Lynch admitted to nerves when he missed an open Bennie Fowler III down the middle with his first pass, but he delivered two, first-down completions to Sanders to start his next series. Operating the hurry-up offense in a series that began with 46 seconds remaining in the first half, Lynch moved the Broncos from their own 33 to the Tampa Bay 19, setting up a McManus field goal from 38 yards away that gave Denver its 17-7 lead entering the intermission.

Can anybody play quarterback in this Kubiak offensive system? An aging Peyton Manning, a rusty Brock Osweiler, an inexperienced Siemian and now an inexperienced and rusty Lynch have all come through when called upon in the last calendar year. The Broncos won Super Bowl 50 last season. They now look like the team to beat for Super Bowl 51 this season.

A quarterback-friendly offensive system?

"You can call it that or you can call it good coaching,'' said Davis, who has played previously for the St. Louis Rams and Cleveland Browns. "It's a system where I feel like guys are put in situations to be successful and that's what you want.''

The coach, naturally, credited the players.

"Plug in? In this league you better plug in good players,'' Kubiak said. "You've got to have great players in this league and get them in position to be successful. I think the kid came in and handled himself really well. We did run the ball better with him in the game, which was important in the second half, trying to keep him out of tough situations.''

Until then, Broncos cornerback Aqib Talib was the hero. On the first series of the game, Talib picked off Winston’s third-down pass at the Tampa Bay 36 and returned it to the 11.

On the Broncos’ first play, Siemian connected with Demaryius Thomas for an 11-yard touchdown. It was Broncos, 7-0. A second Talib interception set up the Broncos' second touchdown, a 1-yard run by C.J. Anderson.

"He got the assist,'' Siemian said of Talib. " When you get those you want to get touchdowns instead of field goals.''

Siemian, was 5 of 7 for 68 yards before the last of the three sacks he took sidelined him for the long day. Sanders and Thomas had their second consecutive big games together. Sanders had eight catches for 88 yards as the game was suspended and Thomas had six catches for 94 yards.

After the weather delay, the Broncos stayed on the ground offensively and let their defense further their relentless attack on quarterback Winston. Derek Wolfe wound up with 2.5 of the Broncos' five sacks.

And now, it appears Lynch will get ready this week for his first NFL start. There is not a definitive diagnosis on Siemian, but any player who suffers an injury that knocks him out of a game almost always doesn't play the next week. Even if it was to his non-throwing shoulder.

Besides, why rush Siemian back when the Broncos want to get a good look at their first-round investment?

"I think on the plane ride you just kind of relax, maybe catch a nap or something on the flight,'' Lynch said. "And then tomorrow we're going to watch the film of this and get moving forward on Atlanta. ... Like I said, I've been preparing like I was going to go out there and play from the first snap in the first preseason game. Up until this point I'm going to just keep preparing and if the opportunity presents itself then I'm ready.''

The Broncos return home to play the 3-1 Atlanta Falcons next Sunday.