Udinese were defeated by two goals in the second half with Erik Falkenburg's tap-in occurring just four minutes after Di Natale's 80th minute introduction. Udinese only managed to muster three attempts on target in the game
But Guidolin stated that he was afraid the 34-year-old striker would suffer from burn-out if he played too many matches. Di Natale has been vital for Udinese's strong showing in the Serie A this season as he has already scored 18 goals in 24 Serie A matches.
Di Natale's manager admitted that he might have made a mistake with the decision to not employ Di Natale from the beginning stating that he believed his side had what it took to overcome the Dutch outfit.
"I make my choices, I know the group and I think I know where we can get the kind of performances that we are capable of making," Guidolin told calciopro.com.
"In the face of defeat, when you leave top scorer in the league on the bench, it is normal to come under criticism.
"I accept that I may have been wrong but I will go my way and make my own decisions.
He also bemoaned Alkmaar's goal against the run of play in the second half that deflated the momentum that Udinese had built up in the second half.
"AZ deserved to take the lead in the first half hour but instead they scored their first goal when we were playing better in the second half.
"Unfortunately, it was not our best performance.
"Qualifying will now be difficult but we'll play our best in the second leg. It will be tough as we lost with a really good team but we will try.
He also defended his defenders and his team's performance and he remains optimistic that despite being two goals down, the Italian side will play far better at home in the return leg next week.
"Ferronetti played well in the game and I liked his performance.
"I have nothing to reproach my boys.
"We will give everything at the Stadio Friuli to try to overturn this result in the second leg."