Jakeem Grant had second-quarter catches of 65 yards for a touchdown and 39 yards to set up a score as Miami Dolphins jumped to a 23-6 first-half lead en route to a 30-9 victory over the Minnesota Vikings in a preseason finale featuring mostly backups on Thursday night at U.S. Bank Stadium in Minneapolis.

Meanwhile, the most significant player to suit up for the Vikings made the dumbest mistake of the game, costing the Vikings a touchdown late in the first half.

Second-year nickel back Mackensie Alexander, who has been given every opportunity to replace departed Captain Munnerlyn, made a nice pass defense on a pass from David Fales to Grant into the end zone on third-and-5 from the Vikings' 13-yard line in the closing minute of the first half.

But the Dolphins were given second life when Alexander was flagged for taunting after getting in Grant's face to gloat. Fales threw a 6-yard touchdown pass to MarQueis Gray on the next play.

One snap later, Vikings quarterback Taylor Heinicke was sacked in the end zone for a safety by Praise Martin-Oguike. The Dolphins led 23-6 with 12 seconds left in the half.

The player Alexander taunted finished the game with 141 yards and a touchdown on four catches.

The Dolphins took the opening kickoff and went 78 yards for a 7-0 lead on Kenyan Drake's 2-yard run. Miami backup quarterback Brandon Doughty, leading a crew of backups, completed only 2 of 5 passes on the drive but drew a pass interference penalty on cornerback Tre Roberson on a fourth-down throw to the goal line.

The only offensive player of note to play for the Vikings was receiver Laquon Treadwell. The 2016 first-round draft pick, who had only one catch a season ago, probably will start the year as the No. 3 receiver.

After Grant's 65-yard score, the Vikings came back with an 8-yard touchdown pass from Heinicke to Caleb Jones. Marshall Koehn, who is competing with Kai Forbath for the Vikings' place-kicker job, pulled the PAT wide left.

Forbath made a 24-yard field goal early in the fourth quarter. But the Dolphins came back and scored on a 19-yard touchdown pass from Fales to Mitch Mathews.