St. John’s couldn’t have gotten off to a worse start in Saturday’s rivalry game against St. Thomas. On the Johnnies’ third play, sure-armed quarterback Jackson Erdmann threw a rare interception. Their second drive fizzled just as quickly, ending in a punt after losing 3 yards on three plays.

“It was less than ideal,’’ Erdmann said of the 14-0 hole the Johnnies fell into at Allianz Field. “It was tough. But we knew we were good, and we knew we were going to come out and just do our stuff once we started clicking. And we did.’’

That stuff — built on Erdmann’s arm, Kai Barber’s legs and a fired-up defense — propelled the No. 4 Johnnies to a 38-20 victory over St. Thomas. St. John’s (6-0, 5-0 MIAC) held the Tommies to six points over the final 48 minutes, 23 seconds, wresting control of the game to win for the second year in a row.

Erdmann found his footing on the grass of St. Paul’s soccer stadium, throwing for 456 yards and three touchdowns. Barber ran for 80 yards and two scores, and the Johnnies defense limited the Tommies (4-2, 3-1) to 171 total yards in the second half.

Before a crowd announced at 19,508, St. Thomas raced to a two-touchdown lead in the game’s first 11:37. The purple-clad fans in the end zone — many of whom wore soccer scarves in school colors, in a nod to the sport usually played at Allianz — sang and danced like a futbol cheering section on a bright, 65-degree day.

All that good cheer eventually drifted to the other end of the stadium, the one filled with red. The Johnnies now have won 22 consecutive regular-season games and 19 in a row in MIAC play.

“A typical St. John’s-St. Thomas game,’’ Johnnies coach Gary Fasching said. “They jumped out to that early lead, but I’m so proud of our guys. They stuck with it.

“We talked all week about our game plan and what we wanted to do, and we never veered from that. These guys just did a great job of hanging in there. Our defense was really stout, in that second half especially.’’

The Johnnies have not lost a regular-season or conference game since the last Tommie-Johnnie tussle in the Twin Cities, in 2017 at Target Field. Saturday, they kept the string going on a field that was a bit slippery at times, in a stadium built for maximum volume.

No. 11 St. Thomas entered the game averaging 53.2 points per game, fourth most in NCAA Division III, and was second in the nation in total offense (545 yards per game). After Tommy Fuller intercepted Erdmann’s second throw of the game — ending his string of 105 passes without an interception — the Tommies finished a 39-yard drive with a touchdown, on a 6-yard pass from Tommy Dolan to Grant Slavik.

They doubled the lead on their next possession, on Josh Parks’ 32-yard scoring run. Then Erdmann, of Rosemount, went to work. His 29-yard touchdown strike to a wide-open Kenneth Udoibok came with one second left in the first quarter, starting a 19-0 Johnnies run.

Erdmann’s line gave him loads of time to throw to a variety of targets. Though the Johnnies’ receiving corps was without injured Andrew VanErp, one of its top players, T.J. Hodge (119 receiving yards) and Ravi Alston (116) led a group of nine players who caught passes.

“Jackson does it better than anybody I’ve seen in this league in forever,’’ Fasching said. “We have four sophomores at wide receiver. For those young guys to rise to the occasion like they did was a real treat to see.’’

St. John’s pulled within 14-13 on Henry Trost’s touchdown run with 1:36 left in the first half. The Johnnies took the lead for the first time at 12:58 of the third quarter, on an Erdmann pass to Tyler Johnson that made the score 19-14.

Parks answered with a 67-yard run that put St. Thomas ahead 20-19. It took the Johnnies only three minutes to seize the lead for good, on Barber’s first touchdown.

St. John’s outgained St. Thomas 563-388 and had 30 first downs to the Tommies’ 16.

“We’re not playing like we should be able to play right now,’’ Tommies coach Glenn Caruso said. “I do not think we finished well today, whether that’s the play, the drive, the game. And I think the other team did.’’