In an offense that features nine returning starters, it was a pair of 18-year-old true freshmen who did most of the damage in the Arizona football team’s first win of the season over an NCAA Division I-A school.

More importantly, the Wildcats (2-3, 1-1 Pacific 10 Conference) got in the win column against a conference opponent, saving their season for the time being.

Arizona head coach Mike Stoops shed his three-running back platoon system for Saturday’s 48-20 win over Washington State (2-3, 0-2), going with a single back.

And Nicolas Grigsby handled the load pretty easily, exploding for 262 all-purpose yards, including 186 from the ground.

The previous season high for rushing yards by a Wildcat tailback was Xavier Smith’s 77 against NAU on Sept. 8.

Tight end Rob Gronkowski also broke out with four catches for a career-high 115 yards and two touchdowns.

“”I think Nic Grigsby and Robbie Gronkowski probably had as good as any two true freshmen performances ever,”” said UA head coach Mike Stoops. “”They’re really special players, and they give our offense a dimension that’s going to be around for a long time.

“”That was fun to see.””

Grigsby averaged 6.2 yards per carry and had 76 yards on nine receptions, including a 22-yard over-the-shoulder grab for a touchdown. Despite 30 carries, he wasn’t tackled for a loss.

“”Nic gives us some speed and quickness back there that’s very unique,”” Stoops said. “”He catches the ball, he understands everything very well. He’s been a big difference in our success.””

Perhaps the only thing that put a damper on Grigsby’s career night was a lost fumble early in the fourth quarter.

“”He’s just got to hold on to that ball,”” said wide receiver Mike Thomas. “”We’re gonna stay on him in practice and make sure he tightens that ball up.””

Cougars head coach Bill Doba said he was surprised by the number of running plays the Wildcats called, as they ranked last in the Pac-10 in rushing offense before the game.

“”We had come out looking to slow down the pass,”” Doba said. “”They ran better than we thought they would.””

The Wildcats put up 567 yards of total offense, which tied for the 10th-best total in school history. The game had nearly 1,000 yards of total offense between both teams, with the Cougars adding 418 of their own.

Quarterback Willie Tuitama continued to break his own records, accumulating six total touchdowns – five through the air and one on a third-quarter quarterback keeper , his second in as many weeks.

Tuitama finished 22-of-31 for 346 yards.

The play of the game came at the beginning of the fourth quarter, after Gronkowski caught a Tuitama pass up the middle around the Cougars’ 30-yard line.

When the 6-foot-6, 270-pound tight end turned around to run toward the end zone, he plowed right over WSU defender Alfonso Jackson.

Gronkowski stumbled and bumbled to a 57-yard touchdown, and Jackson laid on the ground for nearly five minutes with a concussion.

“”I just caught it and started running down the field,”” said Gronkowski, who nearly tripped when stepping into the end zone.

“”‘Big Country,’ man,”” Thomas said of Gronkowski. “”He’s the man. He’s a big bang, a big load. He’s hard to tackle when he gets the ball. He’s a weapon we have. He’s a good stretch down the middle at any point in time that opens up things anywhere else.””

But the game ball went to Grigsby, who gave hope of Arizona featuring a balanced offensive attack.

After the first quarter alone, he totaled more all-purpose yards than any other Arizona running back all season, with 75 rush yards and 27 receiving.

“”Nic did such a good job running that we would have been crazy not to keep running,”” said offensive coordinator Sonny Dykes.

It was an offensive battle for the entire first quarter. The teams scored on three straight drives to start the game, and cornerback Devin Ross broke the streak by intercepting Alex Brink with 12:12 remaining in the second quarter.

Neither team punted until there were six minutes left in the first half.

The Wildcats took a 20-13 lead into halftime after kicker Jason Bondzio missed a 59-yard field goal, the longest attempt of his career. The kick had the distance but sailed barely left of the uprights.

Arizona played with more discipline than in any other game this season. The team’s first penalty didn’t occur until 10 seconds remained in the first half.

The Wildcats finished with 221 rushing yards after totaling 286 entering Saturday.

“”Our offense is unstoppable,”” Grigsby said. “”We’ve just got to keep playing like we played today. If our O-line keeps doing what they’re doing, we’re going to be pretty hard to stop.””

“”Our whole offense is young,”” Grigsby added. “”I feel we’re all going to keep growing and growing and growing as weeks progress and as the year progresses. Starting next week (at Oregon State), we’re going to make a name for ourselves. We’re gonna start opening people’s eyes up.””

Late hits

Stoops spent several hours at University

Medical Center, 1501 N. Campbell Ave., on Friday morning being treated for kidney stones. He will seek further evaluation today, but after the game Saturday he said, “”I’m great. I feel wonderful.”” …

Arizona’s longest play from scrimmage this season came in the third quarter on a 65-yard pass to Terrell Turner, who was stopped at the 1-yard line. …

Safety Dominic Patrick left the game with a sprained knee. Stoops said Saturday he didn’t know how serious the injury was. …

The Wildcats may have their first Pac-10 Player of the Week representative of 2007. Tuitama is a legitimate contender after he finished third in Division I-A in passing yards (346), had the most passing touchdowns (five) and the highest efficiency rating (223.1). Grigsby finished third in rushing yards (186), but his candidacy may be offset by the lack of a rushing touchdown. …

Through five games last year, Arizona scored 60 points. This season, the Wildcats have 160.

– Bobby Stover contributed to this report