Arshavin grateful for Walcott strike
Hosts Reading raced into a 4-0 lead in the first half of the match on Tuesday, with Walcott pulling one back in first-half injury time.
Russia international Arshavin was in fine form for the visitors at the Madejski Stadium, providing three assists as Arsenal scored three second-half goals to level the game at 4-4 before they went on to win in extra time.
And the 31-year-old playmaker feels his side's ability to get back into the tie hinged on Walcott's delicate lob over Adam Federici, as Arsenal's confidence grew in the second half.
"I think it was important that we scored one goal before half-time because it helped us believe that maybe it was possible," he the Arsenal website.
"I think we showed spirit because you cannot come back from 4-0 down if you don't have spirit. Also I think we were lucky and the referee added extra minutes and we equalised at the end of stoppage time."
Arshavin insisted he was not angry with his side's first-half display, suggesting Reading were simply doing everything correctly as Arsenal failed to cope.
"I did not feel frustrated but everything was going wrong and everything was going well for Reading," he said.
"They got in the necessary positions where they could score and they did it.
"To be honest I did not think about when we had to equalise, I just felt that if we had the chance and God will help us, we will make a draw. He helped us and that's why we scored in the last minute.
"I have lost twice 7-1, once I lost 8-3 and once I won 9-3 and now 7-5.
"But this game was one I will remember always because it was from 4-0 down and I don't think anyone here believed that we could come back. But we did it and we deserved to win."