After the Vikings’ starters fell behind 14-0 in the first half of their third preseason game against the San Francisco 49ers on Sunday, coach Mike Zimmer said Tuesday he thought they should play in Thursday’s preseason finale against the Miami Dolphins.

In the end, though, Zimmer decided against it, opting to sit most of the team’s prominent players and preserve the team’s relative state of good health before the start of the regular season next Monday against the New Orleans Saints. What the Vikings were left with instead Thursday night, in a 30-9 loss to the Dolphins, was a listless showing that didn’t provide much of a showcase for fringe players trying to make the roster.

The Dolphins, who also sat most of their starters, posted 223 yards in the first half against the Vikings’ backups, with wide receiver Jakeem Grant totaling 141 receiving yards in the first half alone. Quarterback Taylor Heinicke and tight end Bucky Hodges suffered concussions, and after the Vikings’ first touchdown, kicker Marshall Koehn hurt his chances of wresting a job from Kai Forbath when he pulled an extra point wide left.

“We had too many mistakes tonight,” Zimmer said. “We gave up too many big plays defensively, and then, when we had drives going, we weren’t able to finish. But I think it was a good opportunity for these young guys to get a fourth preseason game in. We got a chance to evaluate a lot of different guys.”

The Vikings put many of their starters through a pregame conditioning workout, sitting center Pat Elflein and guard/tackle Jeremiah Sirles in addition to the players listed on their first-team offense.

Behind a starting offensive line of Rashod Hill, T.J. Clemmings, Zac Kerin, Danny Isidora and Willie Beavers, Heinicke completed only nine of his 20 passes, throwing for 93 yards and running for another 18 while trying to evade steady pressure from the Dolphins’ defense. He was slow to get up after a first-quarter shot in which he hit his head on a defensive lineman’s back, and was sacked in the second quarter when pressure came around Kerin through the middle of the Vikings’ line.

Heinicke, who played through a rib injury in the second half of the Vikings’ comeback win Sunday, eventually left because of a concussion when Praise Martin-Oguike sacked him for a safety at the end of the first half, though Zimmer said he didn’t expect the injury would affect Heinicke in the regular season.

On the defensive side of the ball, the night didn’t deliver a ringing endorsement of the Vikings’ depth at cornerback.

Grant used a quick move to get behind Sam Brown before running away from Jayron Kearse for a 65-yard touchdown in the first quarter, and caught passes of 28 and 39 yards against Jabari Price, who might have given up another big completion to Grant had the receiver been able to hang on to a deep throw.

Second-year cornerback Mackensie Alexander, who figures to begin the season as the nickel corner, was one of the team’s few prominent players to see the field Thursday night. Alexander looked solid in coverage early, and tipped a David Fales pass off a blitz.

But when the 2016 second-rounder broke up a pass for Grant in the end zone, he turned back to go nose-to-nose with the receiver after signaling incomplete. That earned him a taunting penalty to put the Dolphins in a first-and-goal situation, and Fales found former Gopher MarQuies Gray for a touchdown on the next play.

“I don’t think it was very good,” Zimmer said of the penalty. “We had a little discussion about that.”

With his alma mater playing across town at TCF Bank Stadium former Gophers quarterback Mitch Leidner got the final two quarters of work for the Vikings, going 14-for-19 for 129 yards. His attempt to lead a touchdown drive, though, ended when he slipped on a rollout and was touched down for a five-yard loss by Trevor Reilly.

“It’s something you dream about as a kid, growing up in Minnesota,” Leidner said of playing for the Vikings. “Actually, I don’t even know if you dream about this, because it seems like it’s so far away. But for it to actually happen, it’s pretty cool.”

For players such as Leidner and wide receiver Cayleb Jones, who caught nine passes for 127 yards and a touchdown, the next two days will involve plenty of nervous waiting, as the Vikings decide which 37 of their 90 players to release by Saturday afternoon.

In between the Vikings’ shoddy moments on Thursday night, a few players might have done enough to prolong their NFL careers.

“It’s really up to them. They have to go out and be able to prove it,” Zimmer said. “A lot of them had their opportunities, and they either took advantage of it or they didn’t.”