DENVER — Head coach Kevin O'Connell wanted to see the best from the bottom of the Vikings roster, but they were unable to avoid the catastrophic plays — five sacks and a lost fumble returned for a touchdown — during Saturday night's 23-13 preseason finale loss to the Broncos.

Quarterback Sean Mannion started and played the first half, leading the Vikings into Broncos territory on three of five drives. But inside the two-minute warning before halftime, Mannion felt quick pressure and the ball ripped out of his hands by Broncos outside linebacker Baron Browning, who scored 17 yards later. The Vikings fell into a 17-7 hole and didn't climb out.

The Vikings rested 33 players — including 21 starters — in Denver to complete a winless preseason under O'Connell. The Vikings have lost seven straight exhibitions, with their last win coming on Aug. 24, 2019 against Arizona.

"I know our fans would love to see all of our players out there," O'Connell said. "We constantly stress our guys as part of a plan of attack to have them at their absolute best on Sept. 11. I feel like we're right on schedule to do that."

Preseason wins weren't O'Connell's priority heading into Week 1 against the Packers.

Keeping starters healthy was the focus, underscored by five players getting evaluated for injuries on Saturday; four did not return in receiver Bisi Johnson (knee), defensive tackle T.Y. McGill (ankle), receiver Jalen Nailor (concussion) and linebacker Troy Dye (foot).

Johnson will undergo further testing Sunday on his knee, which did "not look good" in preliminary reviews, according to O'Connell. Johnson already overcame a torn ACL last August. O'Connell said he didn't know whether Johnson injured the same knee.

"Anytime you lose players that have had the kind of production and kind of productive camp Bisi has had," O'Connell said, "that sticks with you. I'm crossing my fingers that we get some good news there. No matter what happened tonight, I know we didn't win a game this preseason, but as of tomorrow morning all those records are going to be 0-0."

Mannion, who finished nine of 16 for 121 yards, sustained drives of 10 and 11 plays, but also nearly threw an interception on a third down dropped by Broncos linebacker Alex Singleton.

"I feel like I've done a good job," said Mannion, who completed 27 of 43 passes for 265 yards and no touchdowns or interceptions this preseason. "Tried to put my best foot forward every day, and I think I've done that."

Quarterback Kellen Mond started the second half and, after two straight three-and-out series, found a spark on the Vikings' longest play of the preseason: a sharply-thrown, 30-yard deep ball to receiver Ihmir Smith-Marsette.

But one step forward was followed by two steps back. Later in the drive, Mond saw quick pressure up the middle and took a third-down sack. Kicker Greg Joseph saved the possession with a 58-yard field goal in the fourth quarter.

Mond rekindled the spark on his next drive, completing four straight throws for 47 yards to bring the Vikings into the red zone. He then took a fourth-and-goal sack, killing the drive. Mannion and Mond took a combined five sacks.

Quarterback Nate Mullens, acquired five days earlier via trade with the Raiders, suited up as an "emergency" option but did not play, per O'Connell. Mullens said he was told Saturday morning he wouldn't play against the Broncos.

"I didn't want to throw him out there just yet," O'Connell said. "We'll continue to talk about what that depth chart is going to look like behind Kirk."

Broncos running back Mike Boone, the former Vikings reserve, ran with a purpose churning out 51 yards on seven touches in the first quarter. Boone shed safety Josh Metellus and Dye on a 4-yard catch and run that set up an early Broncos fourth-down conversion.

O'Connell's first challenge with the Vikings put points on the board.

He wanted officials to take another look after running back Bryant Koback appeared to be stonewalled on a fourth-and-goal run. Further review showed Koback crossed over during the goal-line collision, giving the Vikings a 7-3 lead in the second quarter.

The Broncos quickly responded with a five-play, 70-yard touchdown drive, sparked by a 45-yard bomb from Broncos quarterback Brett Rypien to receiver Seth Williams with cornerback Kris Boyd trailing. Boyd earlier had back-to-back pass deflections to stall a Broncos drive in Vikings territory.

Final evaluations will give way to roster decisions this week. Some competitions for backup jobs — like receiver and inside linebacker — remain murky because of injuries. Johnson had "earned the right" to be on the team, according to O'Connell, but is the latest to get injured.

"Nailor has had a really strong camp," O'Connell said. "Had some real flashes [Saturday night]. Just with the rest of the depth with Ihmir [Smith-Marsette], Trishton [Jackson], and obviously Myron [Mitchell], we didn't get to see a lot of Dan Chisena. There's still some real quality behind those first three that we're going to have some hard conversations about."

The roster needs to be trimmed to 53 players by Tuesday afternoon; 27 roster moves are required. Up to 16 players may be re-signed onto the practice squad, which can be set Wednesday.