The talismanic Owls forward was left devastated after Carlos Carvalhal’s men lost on penalties to eventual winners Huddersfield Town in the semi-finals last month.
Forestieri stepped up to take Wednesday’s fifth spot-kick in the shootout but Danny Ward kept out his weak effort to send the Terriers to Wembley.
The Argentine-born player issued an apology to the fans and described his penalty miss as “the worst feeling” of his life.
“I saw Fernando’s face the day after the game,” said Owls coach Lee Bullen. “The kid was distraught but there was a glint of determination in his eyes. I just feel this will make him even more determined. He is a tough little bugger.”
Forestieri endured a mixed season. He finished the Owls’ top-scorer, claiming 12 league goals in 25 starts.
His refusal to play at Norwich City brought uncessary negativity and his performances lacked consistency.
He was used sparingly in the final two months due to a knee injury.
But head coach Carlos Carvalhal turned to Forestieri in the end-of-season decider.
Forestieri, who has frequently tormented Huddersfield over the years, struggled to make an impact in the first leg.
Despite Forestieri’s below-par display, Carvalhal kept faith with him at Hillsborough and the former Watford man was a lively figure throughout.
Bullen believes Forestieri gives the Owls’ attack an unpredictable edge and is backing him to be a key man next season.
Speaking at a recent question and answer session organised by Steel City Memorabilia to raise funds for Bluebell Wood Hospice, Bullen said: “Fernando is happy if he is playing in the team. At the back end of the season, we had to basically manage him properly with his injury. We had to throw caution to the wind and play him (in the play-offs).
“Fernando is one of the best players in the Championship. He is our Anthony Knockaert because he is something different. He can make or score a goal out of nothing.
“Sometimes you have to go with that maverick character. Fernando gives you that X-Factor.”