Up until then Basel were leading on the night and, according to Streller, playing good football.
However, in the second half he said that Chelsea's tempo was too much and after the third goal Basel "were dead".
"I don't know what happened in the second half," Streller told UEFA.com. "They scored with two counter-attacks and then the third goal was amazing, and after that we were dead.
"However, the first half was very good. We had chances and Chelsea also had chances and in the end it's clear Chelsea are an amazing team and I think they will beat Benfica in the final.
"I think they are better in terms of individual skill and also in terms of experience. They have world-class players who are used to this type of game while for us it was our first time in the semi-finals, and that was a key to Chelsea's win."
Chelsea will meet Benfica, who beat Fenerbahce 3-2 on aggregate, in the final.