POTOSI, Wis. - It was one of 54 plays run by the De Soto High School football team's offense on Saturday, but there's no doubt it was the biggest.

The Pirates had just been given a second chance, and Dylan Vassar and Dylan Tully made the most of it on the most basic of passing plays.

As Vassar stood in the pocket against three unblocked pass rushers, Tully floated toward the left sideline. The screen pass isn't a normal call for the Pirates, but they had a hunch it could work in the fourth quarter of a close WIAA Division 7 state quarterfinal game against Potosi.

Vassar's ability to deliver the ball and Tully's ability to turn it into a 48-yard gain set up a go-ahead touchdown that was the key in the Pirates' 21-7 victory over the previously unbeaten Chieftains.

"We were throwing the ball a lot, and we knew they'd have to bring some people after (Vassar) eventually," De Soto coach Ev Wick said of the successful screen. "When we hit that one, it kind of jump-started us."

The victory gets De Soto (12-0) another shot at Burlington Catholic Central (11-1), which beat the Pirates in last year's semifinals before winning the state title. The game will be played Friday night in Middleton, Wis.

Tully cut behind two big blocks on the 48-yard gain, which gave the Pirates a first down at the Potosi 4-yard line in a game the Chieftains led 7-6. The next play lost 2 yards, but Tully's 6-yard touchdown run on second-and-goal gave De Soto the lead for good with 9 minutes, 14 seconds left.

The play only took place because a Potosi penalty nullified a Vassar interception on the first play of the drive. Sean Sparrgrove's interception was taken away when one of the Chieftains was called for a shot to Vassar's head on the play.

The 15-yard penalty gave De Soto a first down at its own 46, and Vassar and Tully connected on the screen pass three plays later.

The Chieftains (11-1) went three-and-out on their next series, and De Soto senior Chad Johnson ended the next one by sacking quarterback Rockie Reuter for a 10-yard loss on fourth-and-7 from the Potosi 30 with 3:23 left.

"I gave it everything I had because that was a big play," said Johnson, who also sacked Reuter for a 14-yard loss early in the game. "I hit a move quick and got by (lineman Steven Ward), and there (Reuter) was. We needed that play."

Johnson, Andy Lee, Frank Ames and Eric Peterson all made tackles behind the line of scrimmage for the Pirates, who only gave up an 85-yard touchdown drive in the second quarter.

Lee, who caught four passes for 43 yards, had a touchdown catch in the third quarter and a touchdown run in the fourth. Vassar passed for 246 yards and completed 15 of 22 passes.

Vassar's game was needed against a defensive line that included Potosi junior Cole Mish - all 6 feet, 6 inches and 320 pounds of him - and was tough to run on all day.

"It took us a while to figure out how to get anything with the running game," said Wick, whose team rushed for 59 yards on 32 attempts. "Six-six, 320 in the middle doesn't help, but our running game was a little more effective in the second half because (Vassar) was able to throw."