EAST RUTHERFORD, N.J. -- Perrish Cox took umbrage earlier in the week with the notion that he flopped on the Hail Mary catch made by Jimmy Graham, which was nullified after Graham was called for offensive pass interference for shoving the San Francisco 49ers cornerback.

"I was mad because I was focusing on another pick," said Cox, who leads the 49ers with four interceptions. "I wasn't even thinking of flopping."

If no flags fly, the New Orleans Saints win the game on the final play of regulation. But with the, ahem, shove, which, Cox added, contributed to a sore hip from when he hit the Superdome's artificial turf, the 49ers were able to go to overtime, win and stay within reach of the Arizona Cardinals and Seattle Seahawks in the NFC West.

"I threw my hands up at the same time," Cox said, "to show the refs I was shoved."

There is no debating this, though: Cox has been one of the biggest surprises on defense for the 49ers thus far.

Orginally slated to be the third cornerback, Cox was pressed into action when Tramaine Brock injured a toe in the season opener. Brock has been slow to return from the injury.

"Perrish Cox has been a great story this year," 49ers defensive coordinator Vic Fangio said. "I remember calling him into camp prior to the start of camp and talking to him and telling him what he needed to do to make this team, because at that point there was no guarantee he was going to make this team. And I figured I'd have to call him in in another couple weeks to remind him because he might slack off, but I never did. Never did have to. He did exactly what I told him he had to do.

"He had laser focus and got it done. And when camp was over and he made the team, I brought him in and I congratulated him for doing exactly what he had to do."

Cox has also played for Seattle and Denver and his previous stint with the Niners left a certain impression on Fangio that made him think Cox would "slack off."

Why, exactly?

"Been his history," Fangio said.

It has not been an issue this season, though.

"Yeah, I think it's a little bit of everything," Fangio said. "Players improve over time, OK, until they get older and then they have to maintain. He's still in the improving stage. I think he matured emotionally and mentally. I think playing him at corner has helped him. I think it's everything. I don't think it's one thing."

One thing Cox might have to add to his repertoire this weekend, though, is his skill as a punt returner. He replaced Bruce Ellington last week in New Orleans when Ellington injured his ankle against the Saints. The rookie did not practice this week and is listed as questionable to play against the New York Giants.

"He's done a tremendous job for us," Fangio said of Cox, "and [I'm] really happy for him as an individual."