Real Madrid were bounced out of the Club World Cup at the semifinal stage by PSG, losing 4-0 on Wednesday.
Despite the heavy defeat, Guti told DAZN: "Xabi knows that as Real Madrid manager, everything counts. But I'm with him, I'm with him.
"You can't judge Xabi Alonso's work in this Club World Cup by everything we've said, it's true that he lets it slip, that we'll see another Real Madrid and I'm convinced that's how it will be."
Best right-back in the world
Guti also had a word for PSG wing-back Achraf Hakimi, who he coached inside Real Madrid's academy.
He said, "Achraf is a spectacle, he already was when he came down, when he told me 'hey, let's see if I can play', I said 'but how? Let's see if we can keep you here', because it was a spectacle to watch him play.
"It's incredible how much he's matured, in the moment he's with his team and him personally... It's a spectacle to watch him, I've already told him when the match is over and I'm telling him now, for me right now he's the best right-back in the world."