Pressed further on whether Pulisic can be considered world-class after finding consistency on form and fitness fronts, Keller added: "It starts the other way, it’s fitness-form. At least it was at Chelsea. That’s the part, and he has a little knock right now that doesn’t look like it’s going to be a big deal. There has to be that point, and I think a lot of managers will tell you, sporting directors when they are looking to buy players, there has to be this trust that you are going to be available for the majority of matches.
"Plenty of players have gone through injury issues and then it has to be that situation where you have to rebuild that trust and the manager says ‘I can make this commitment because I know that nine out of 10 times you are going to be fit to be in the squad’. Do you know how hard it is as a manager to start making plans and tactics, how you are going to play, and then the player that fits into your tactic is never fit to play and then you have to adjust everything because nobody else can play like that in your system? I understand why there is that apprehension at times.
"All you can do as a player is go out and stay fit. It’s easier said than done because when you are a skilful player, somebody is going to boot you every once in a while - which happens! I’m really proud of what he’s done. He’s reset by basically just saying ‘I can stay fit, I can play not only at the highest level week in, week out in the league but I can also do it in Europe’."