LAST-SECOND FG KNOCKS OFF CAL By RON BERGMAN Mercury News Staff Writer SAN DIEGO -- Cal Coach Keith Gilbertson watched Peter Holt's 32-yard field goal go through the uprights at the gun Saturday night before making the lonely trudge to the losers' locker room. ''Mistake, mistake, mistake,'' Gilbertson said after the Bears were upset in their opener by San Diego State 22-20. ''Penalty, penalty, penalty. Dropped ball, dropped ball, dropped ball. It's just a nightmare.'' That's the way it went before 40,922 fans at Jack Murphy Stadium. Just when it looked as though the Bears were going to get out of Dodge alive, they'd do something so dumb, you'd want to run their SAT scores through the computer one more time just to make sure they really met the admission standards at Berkeley. Even when the Bears did something right, they'd foul it up with something wrong. After taking a 20-19 lead on a 10-yard TD pass from Dave Barr to third-string tight end Marc Vera with 5 minutes, 4 seconds to go in the game, Cal seemed to clinch its fifth straight opening-day victory. Aztecs quarterback Tim Gutierrez threw a strike to Will Blackwell. But the ball went off the receiver's pads into the hands of safety Ricky Spears for an interception. Spears ran the ball back inside the San Diego 5. But someone away from the play was detected blocking from behind on the runback. The penalty took the ball out to the 22. Reynard Rutherford, who rushed for 109 yards in 29 carries, ran for 5. He fumbled, but teammate Randy Nohnof recovered. Barr missed on a fade to Iheanyi Uwaezuoke before planting a pass right in the mitts of fullback Marshall Foran. Foran flat-out dropped the ball. Instead of a first down, the Bears were forced to call on Ryan Longwell to attempt a 34-yard field goal. He already had connected from 42 and 43 yards. This time, he missed wide left. The Aztecs took over on their 20 with 3:22 remaining. Running back Wayne Pittman gained 8 on second and 10, but the ball went to the San Diego 42 when a Cal player was caught shoving tight end Marc Ziegler in the back. The Bears continued to unravel until Holt kicked the ball through for the winning points. Cal safety Matt Clizbe would like to forget the first half. His two gaffes on the same series kept the game close. The Bears had taken a 3-0 lead on their second offensive series when Longwell punctuated the drive with his 42-yarder. The Aztecs took over and appeared to be stalled when Gutierrez threw an interception under pressure from Clizbe's safety blitz. But Clizbe clipped Gutierrez in the head with his hand on the way past and the Bears were penalized 15 yards. San Diego State couldn't move the ball and punted. Clizbe, one of the more sure-handed returners, decided to run with the ball before he really had it. The next thing anyone knew, the Aztecs' Eric Sutton had recovered the fumble on Cal's 19. Five plays later, San Diego was in the end zone, thanks to a play-action pass to backup tailback Ken Overby for 2 yards. The big play in the short drive was a 19-yard pass to Ray Peterson on second and 13 from the 22. The Bears stalled again on their first series of the second quarter. But the strong-footed Longwell, who has taken over for the graduated Doug Brien, brought the Bears to within 7-6 with a 43-yard field goal. Clizbe figured in the Bears' lone TD drive of the first half. Back to field a punt, Clizbe was bowled over by Derek Norman while calling for a fair catch. The 5-yard penalty got the Bears started from their 29-yard line. Barr began quickly, with an 18-yard strike to Uwaezuoke. Later in the drive, former defensive back Tyrone Edwards, now a tailback and fullback, snapped off a 15-yard run that ended up with the ball on the 11 because of a personal-foul penalty. Three plays later, Barr had his choice of two wide-open wide receivers. He chose Uwaezuoke while Na'il Benjamin stood alongside and watched the touchdown. A two-point conversion pass to Edwards gave the Bears a 14-7 lead at intermission. The Bears couldn't generate any consistent offense in the third period when they managed only two first downs. By all rights, the Bears would have fallen behind earlier in the third period. But Curtis Shearer, who had gotten behind left corner Kevin Devine, dropped a sure touchdown pass that would have gone for 67 yards. The Aztecs had to settle for a 23-yard field goal by Peter Holt, the first of two for him in the quarter that brought San Diego State to within 14-13. On their next possession, the Aztecs struck on second and 10 from the San Diego 35 when Gutierrez spotted split end Will Blackwell in single coverage by corner Artis Houston. Houston went for the interception, a mistake that left him pounding his chest in remorse. Blackwell caught the ball on the Cal 40 and went the rest of the way untouched for the TD that put San Diego ahead for the first time in the game. The two-point conversion pass was ruled no good after Houston and Shearer tripped over each other in the end zone.