Valdes had already seen one penalty saved, as had Stevan Jovetic, when he stepped up to earn a 1-1 draw.
"He showed great character and courage, as he went to take the decisive penalty after failing to convert another. I am happy," said the Coach.
"It is always important that everyone who goes on to the field gives their all and at the end the results will come.
"Today we did not give Fiorentina many opportunities, even though they had a lot of possession. My lads had the right approach.
"In the second half we did well and Antonio Mirante's penalty save on Jovetic gave us that extra push to fight back for the point.
"We have got to believe in ourselves more, though."