Faizulin, appearing in only his second international after making his debut in last month's friendly against Ivory Coast, put the home side ahead with a fine strike on the half-hour in Capello's first competitive match in charge.
"I think we could have scored more but 2-0 is not too bad also," the Italian, who replaced Dutchman Dick Advocaat as Russia coach last month following their disappointing showing at Euro 2012, told a news conference.
"We were a bit tight in the first 15-20 minutes but then played much better. In general, we didn't have any problems tonight, so I'm pleased with the team's performance."
It was the first competitive match for Michael O'Neill at the helm of Northern Ireland following three friendlies and he was disappointed by the display.
"We're disappointed to lose the game. We were disappointing in our possession at times. We had to work so hard off the ball," he said. "As for the penalty, I don't think it should have been called."
Russia's win maintained their unbeaten record against Northern Ireland, who managed two draws and two defeats in four World Cup and European Championship qualifiers against the former Soviet Union.
