By FOX Sports staff
Inter recorded a 2-0 win over Cluj on Thursday at the San Siro before succumbing to a lethargic performance in the three goal defeat to Viola three days later.
"I think it's clear what happened today [Sunday]," Stramaccioni told the club's website.
"Regardless of the merits of our opponents, I think we paid for the Europa League match in midweek.
"Probably I myself hadn't imagined what would happen after having played two games with the same players. And, while being able to foresee it, I never imagined we would have paid so dearly.
"When you're always a step late to the ball... my lads looked very tired to me. Again, this all comes from my assessment, and I never thought we would have paid for it so much."
Fiorentina got the goals from Adem Ljajic and Stevan Jovetic, who both bagged two goals apiece, while Antonio Cassano scored a fine consolation goal in the 86th minute.
"This Inter was too ugly to be true, but I think it's possible to have a heavy defeat like this in the league," Stramaccioni said.
He added: "I honestly don't think it's a problem regarding individuals because eight of these starters were coming off of positive performances."
"To discuss individuals now wouldn't be productive. I think everyone had a sub par performance."
Inter must now picked themselves up in time for the second Derby della Madonnina of the season next Sunday against AC Milan.