UCI got the better of play in the opening half, when it posted a 7-3 advantage in shots.
But Northridge (7-7-2, 3-3-1) came at the defending conference regular-season champions in waves in the second 45 minutes, drawing sporadic roars from the home rooters.
UCI had 16 shots in regulation to the hosts' 14, and the Matadors accounted for all three shots in the two 10-minute extra sessions to finish with a 17-16 edge in that category.
"I think a point tonight [for the tie] was a fair result for that type of game," said UCI Coach George Kuntz, whose team defeated Northridge, 2-0, at home on Oct. 8. "Both teams decided to play more defensive. There were times when they had chances and times when we had chances. It was a bare-knuckle game."
It was the third straight overtime game for UCI, the second straight shutout. UCI is now 3-1-1 in overtime games.
Northridge is 0-3-2 in overtime contests.
"We knew we had to play great defense," Kuntz said. "For us, the shutout is very good, because this is a process. [The last] two games without a goal is good for us and we want to keep that going defensively. I thought that was a big plus for us. I was happy with that."
Senior midfielder Jimmy Turner, sophomore midfielder Christopher Santana and senior midfielder Miguel Ibarra had three shots each to pace the UCI offensive attack.
UCI played without sophomore midfielder Enrique Cardenas, who has been sidelined by a strained knee sustained against UCSB on Oct. 1.
"We've been taking everybody's best shot all year," Kuntz said. "To do it for eight weeks with such a young team is pretty darn good. It was a good soccer game; a real tactical game for both teams."
Kuntz said Fontein, who got was tested more thoroughly than his two saves might indicate, was better than good.
"He had a couple really good saves and I'm happy for him," Kuntz said.
UCI was also bolstered by the four-man back line of senior Bello Alhassan, junior Everett Pitts and sophomores Marco Franco and Jake Marcon.
Northridge, coming off a 3-2 upset win at then-No. 8-ranked UCLA, the Matadors' first road win over the Bruins, remain in fourth place with 10 points.
UC Davis has 15 points, UC Riverside has 11 points and UCSB and Cal Poly San Luis Obispo each have nine points as the battle for four Big West Tournament berths goes down the stretch.
"We'll take it for now," Kuntz said of his team's spot atop the conference standings. "
Brian Behrad had four shot attempts to pace the Matadors, who received six saves from junior goalkeeper Michael Abalos.