Colorado wide receiver Brenden Rice, left, hauls in a touchdown pass against Arizona during Saturday’s game in Boulder. The Buffaloes extended Arizona’s losing streak to 18 games.

 Geneva Heffernan, Associated Press

BOULDER, Colo. — Just when you thought it couldn’t get any worse, Part II:

Arizona lost to Colorado on Saturday, and it wasn’t close.

The Buffaloes — who had one win, over an FCS school — defeated the Wildcats 34-0 at Folsom Field, handing Arizona its 18th consecutive loss. It was a six-point game midway through the third quarter. Then the Wildcats fell apart.

In a span of just over five minutes, Arizona surrendered a blocked punt that was returned for a touchdown; threw an interception that was returned for a TD; and allowed a 62-yard touchdown pass.

Just like that, what seemed like the Wildcats’ best hope to end their losing streak vanished. Arizona (0-6, 0-3 Pac-12) last won a game on Oct. 5, 2019, at Colorado.

“Very tough game for us today,” first-year UA coach Jedd Fisch said afterward. “Need to play better. Need to coach better. Really need to improve in every single area.”

The Wildcats were shut out for the first time since a 49-0 loss to Oregon on Sept. 22, 2012.

UConn’s victory over Yale earlier Saturday left two winless teams in FBS: Arizona and UNLV. The Runnin’ Rebels were set to host Utah State later Saturday.

Arizona is halfway through its season. Fisch told the players that they have an entire second half to make something positive happen.

“I’ve never been part of a game — played, coached, whatever it might be — that at halftime, you don’t say the score is 0-0,” Fisch said. “That’s our mentality.

“The first half didn’t go the way we wanted. Now we got the second half to go out and (have) the best second half of the season we can have.”

Colorado running back Jarek Broussard, center, is dragged down after a short gain by Arizona linebackers Anthony Pandy, left, and Jerry Roberts.

Arizona’s next chance to end the skid comes Friday night against Washington. The Wildcats will have yet another new starter at quarterback.

Gunner Cruz struggled against Colorado after regaining the job following a season-ending injury to Jordan McCloud. Cruz had just 82 yards when he threw an interception in the third quarter that Carson Wells returned 50 yards for a touchdown.

Cruz injured his thumb on that play, banging it on a helmet. Fisch said Cruz likely will be out the rest of the season — meaning Arizona has lost a quarterback to a season-ending injury in back-to-back weeks.

Fisch had no choice but to insert Will Plummer, who had relieved Cruz at a similar juncture against San Diego State in Week 2. Plummer started the following week against NAU but was pulled after throwing a second interception. McCloud then took over and performed the best of the three by far. He was lost for the season in the fourth quarter of last week’s game against UCLA.

“We’re in the middle of growing pains, playing with young quarterbacks that have not had a lot of playing experience,” Fisch said “That’s, unfortunately, where we are at.”

The pick-six was part of a horrific sequence late in the third quarter. It began with Colorado’s Trevor Woods blocking a Kyle Ostendorp punt, scooping up the ball and taking it 36 yards for a touchdown. It was the second blocked-punt TD allowed by the Wildcats this season. Arizona nearly had a punt blocked against UCLA last week.

Cornerback Isaiah Rutherford got beat on the 62-yard TD pass from Brendon Lewis to Brenden Rice. It was one of few major miscues by the UA defense, which played well enough to win — if the offense had provided any support whatsoever.

Colorado linebacker Carson Wells celebrates as he crosses into the end zone to score a touchdown following an interception of Arizona’s Gunner Cruz.

Colorado (2-4, 1-2) entered the game averaging a league-low 13.8 points per game. Lewis was averaging just 95 yards passing. He finished with 248. But the Buffs offense scored only two touchdowns — the second after the game had been decided.

Defensive tackle Kyon Barrs took no solace in the defense’s performance, which included limiting an opponent to less than 400 yards (365) for the fourth time this season.

“We’re all a team,” Barrs said. “If they mess up, we mess up. If they do good, we do good.”

Colorado took a 3-0 lead on its opening possession. It easily could have been more.

Dimitri Stanley dropped a would-be touchdown pass in the end zone. The Buffaloes advanced the ball to the 1, but Karl Dorrell elected to kick a field on fourth-and-goal. Cole Becker punched it through from 19 yards.

Another field goal, this one a 37-yarder by Becker, made it 6-0 midway through the second period. A coverage bust set up the score. Leevel Tatum III had pressure on Lewis near the sideline, but the Wildcats left tailback Alex Fontenot open downfield for a 43-yard gain.

Later in the quarter, Arizona came as close to scoring as possible without doing so. A fourth-down conversion, a pair of penalties and a 23-yard run by Jalen John set up first-and-goal at the 1. The Wildcats couldn’t get in the end zone.

A sneak by Cruz and two John runs netted 0 yards. On fourth down, Cruz rolled to his right but couldn’t connect with a tightly covered Alex Lines.

“It was definitely a little bit frustrating,” said John, who finished with a career-best 71 yards. “It just comes down to us finishing our blocks, and then making sure we all come together and do what we gotta do to punch it in.”

Colorado wide receiver Dimitri Stanley, right, drops a pass in the end zone as Arizona safety Jaxen Turner defends during Saturday’s first half.

Overall in the first half, Arizona had five first-down plays that lost yardage — and another that went for no gain (first-and-goal from the 1). Not coincidentally, the Wildcats also faced five third downs of 9 yards or greater.

That happened four more times in the second half. Arizona didn’t converted any of them.

On their final possession, the Wildcats faced fourth-and-12 from the Colorado 20. Fisch eschewed a field goal that could have averted the shutout. Plummer threw a pass into the end zone for receiver Jalen Johnson. It was broken up.

Fisch said there was no finger-pointing in the locker room after the game. Everyone wants the same thing — to end the skid.

“I challenged the team to go out there and find a way to get better,” Fisch said. “What else can you do you? Why else do you play the sport? Why else do you participate in a team sport like this other than to go find a way to keep competing and keep competing and keep competing?

“Yeah, it’s hard right now. But it is what it is in terms of what’s gone on in the past. All we can control is what goes on Friday night. Our job against Washington is to play our best game of football and to do everything we humanly, possibly can to move the football and get a victory.”

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Contact sports reporter Michael Lev at 573-4148 or mlev@tucson.com. On Twitter @michaeljlev