Casillas was forced to sit in the dugout during the Euro 2016 as former coach Vicente Del Bosque put his trust in Manchester United's David de Gea for first team duty, reports Xinhua.
Defending champions Spain were beaten by Italy in the quarter-finals. Casillas captained Spain to two Euro triumphs (2008, 2012) and a Wold Cup (2010) in a trophy-filled illustrious career.
After the tournament and his subsequent resignation Del Bosque said Casillas was the only player he had not informed after stepping down from his post.
Del Bosque said the 35-year-old had behaved well to his companions but that his "behaviour was not good", with his coaching staff.
One of Lopetegui's first decisions as a coach will be whether or not to keep Casillas in the fold or to bring in a younger keeper.
Lopetegui's fresh comments indicate that Casillas' international career could be over.
"I haven't spoken to Casillas yet," admitted Lopetegui, who said he had spoken to other players.
"What happened in the 2016 Euro is in the past and I wasn't there and am not going to give an opinion, however, I am not going to look backwards and my first criteria for selecting my side will be the form that players are in now, rather than the trajectory of players who have left their mark on an era," continued the coach.
"We have to respect the players who have left their mark on the Spain team and Casillas is one of them. I respect everything he has done and the effort he has made for the team."
"But I will not take decisions based on that, I will take them based on form, be it for Casillas or anyone else," insisted Lopetegui.
