Lopetegui was sacked by Madrid on Monday, with a 5-1 Clasico defeat to Barcelona drawing the curtain on a disastrous four-month tenure.
Real Madrid Castilla boss Solari took over as caretaker, and goals from Karim Benzema, Marco Asensio, Alvaro Odriozola and Cristo Gonzalez ensured his tenure got off to a comfortable start.
And Solari was pleased with the desire shown by Madrid's players – in particular Sergio Ramos – to make things right in the wake of Lopetegui's departure.
"The team played with joy, enthusiasm and commitment and the result is the fruit of that," Solari told a news conference.
"They are great champions, they are very committed. If not, you do not earn everything you have earned.
"They are hurt because this is sport, there are dynamics that are bad and it has to be reversed. We have done many things well.
"I'm happy with the team's character, they ran, they looked for the goal, they were fresh and happy.
"Ramos, it was very important that he came, showing that you had to pull the team at a time like this.
"You win with courage, sacrifice. The boys did a great job."
Vinicius Junior was one of several Castilla regulars drafted into the first-team for the clash in north Africa, setting up two of Madrid's goals on his first official start.
But despite being impressed by the youngster's performance, Solari stressed the need for patience.
"I'm happy with how he did it, like the rest of the team, but Vinicius is very young, he's very talented, but he's just arrived, he's only 18," Solari said.
"He is adapting to a new country, to a new continent, to Real Madrid, which is a world in itself, and to another culture, other friends.
"He has many things to learn. We see talent, but football is made up of more."