The season's opening match against Burnley, which ended in a 1-0 victory, was only Llorente's second game for the club.
In the end, the £5m signing could not do enough to save his manager Guidolin, who was sacked after the Swans did not win in their next six matches.
However, the Italian believes it was not the play of Llorente, but the timing of his arrival, that cost him his job.
He told Tribalfootball.com: "What would I do differently with Swansea? A big regret was the one related to Llorente, it was decisive.
"We needed an important striker, since we would have played with a striker and Sigurdsson as number 10. I knew Llorente for what he did in Italy, in Europe, he is a champion, but he needed to train because he had played little in the previous season and needed to interact with the team soon.
"He came right to the end of the market, I had little time to get him to find the form and to put it in the tactical team context."
Now seeing Llorente's heroics in the Champions League with Tottenham, Guidolin isn't surprised after his short time with the Spaniard.
"In the long run, when unfortunately I was no longer there and thanks to Fernando, the player started to turn and made 15 goals. With Sigurdsson, the two most important offensive players, they have made an important contribution to the safety of the team. If I could go back, I would have liked Fernando at least 3-4 weeks before."