He said: "I didn't know what to think when my penalty kick hit the crossbar. At first, I thought it crossed the line but the referee said it didn't so it was really disappointing as I walked back to the rest of the players.
"It's hard to say what was going through my mind. I knew we were playing for a place in the group stage and that it was very important to the club, the players and the supporters.
"I'm lucky Artur (Boruc) made the saves and got us through. He came to the rescue and I was very relieved to see him make them. It was a great feeling to qualify."
However, even as Naka reflected on the joy of edging out Spartak, he was still upset at himself for not making a bigger impact.
He said: "I missed two good chances during normal play and Jan Vennegoor of Hesselink missed a penalty. On another day, we would have scored the goals and won the game.
"However, I am not happy with missing the chances. I've been thinking about it a lot since the end of the match.
"But it was a really difficult game. We had better chances than Spartak, but they passed the ball well and played on the counter-attack. They have quick players and were dangerous.
"After taking the lead we were looking to get to half-time with the one-goal advantage, but then we lost a bad goal."