Trailing 2-0 at halfime, Simons was influential as Spurs fought back through a double from Dominic Solanke.
On Simons, Frank remarked afterwards: "I think Xavi was exceptional today. He's a very good footballer. But he's probably an even bigger winner and fighter. So the way he fights with the team is exceptional. And how he's part of driving the team forward I think is very impressive.
"I think it's fair to say that the Premier League is the best league in the world. It's also the most physical, not only in the duels, but physical in the pace of the game.It's so quick. And to adapt to that takes a little bit of time. And then I think some players, for whatever reason, just adapt a little bit quicker.
"For whatever reason, if they're coming into a team that's in flow, they may adapt a little bit quicker. There can be a lot of things. And it's humans we're dealing with.
"The most important thing is their intentions and their work ethic and all that. And then it'll be step by step. And I think Xavi has taken some big steps, especially in recent weeks."