This, as well as a penalty kick that amounted to the Mustangs' lone shot on goal, allowed the unranked visitors to post a 1-0 men's soccer upset of the No. 7-ranked Anteaters.
The win also left Cal Poly with a piece of the Big West lead.
"Everything," UCI Coach George Kuntz said of well-positioned Cal Poly defenders, who helped the visitors (4-3-2) stave off an 18-3 shot disadvantage. "They got a piece of everything, and that's their deal. You've got to give them a lot of credit."
While generous with praise of the Mustangs' stingy defense, Kuntz said the Anteaters (8-2) have mostly themselves to blame for myriad missed scoring chances.
"We've got to finish our opportunities," said Kuntz, whose team played with 11 players against 10 after a second yellow card to the same player prompted a Mustang ejection in the 57th minute. "I think we played a bit young tonight. With a fairly young team, you're going to have fairly erratic nights. And this was one of them. Most of the season we've been finishing, as one of the leading scoring teams in the nation."
UCI came in having scored 22 goals in its first nine games to rank No. 3 in the nation in total goals and No. 10 in scoring offense.
Cal Poly, on the other hand, had tallied just six goals coming in, one fewer than its opponents this season.
Kuntz said a lack of composure, as well as an officiating trend that allowed Cal Poly to play its physical style against the smaller Anteaters, helped his team come up short.
"When we had a man advantage, we played with more urgency and more recklessly than we had to," Kuntz said. "We need to play with more composure and that's one of the lessons from tonight.
"Another lesson is that you can out-play and dominate a team, in style and everything. But style points don't count here. And, when you get a goal, it can change the game."
Cal Poly took advantage of its only serious scoring threat, when senior Patrick Sigler powered a low drive inside the left post on a penalty kick in the 53rd minute.
The PK was created when UCI senior defender Jonathan Rivas was called for a foul while taking down a Cal Poly attacker inside the 18-yard box.
UCI senior goalkeeper Andrew Fontein finished with no saves, while his counterpart, freshman Chase Hauser, had eight saves to record his fifth shutout of the season.
It was only the second time UCI had been blanked all season, but the second time in the last three contests, including a 2-0 loss at South Florida on Sept. 18.
Senior Christian Hernandez had five shots for UCI, for which sophomore Enrique Cardenas fired three shots.
Cardenas had the best chance, punching a point-blank offering that Hauser hauled in the center of the posts. The chance was created by a deft pair of passes from Hernandez and sophomore Marco Franco in the 63rd minute.
It was the second straight loss against a Big West opponent for UCI, which has lost three of its last four against conference foes. That run followed a 10-game unbeaten streak against conference rivals.
"The good news is, we've got a long way to go," Kuntz said. "It's the beginning of league and its better to get our lessons here than later. We're playing in front of a great crowd on Saturday. Hopefully, we rise to the occasion."