The full-back has missed the Foxes preparations due to England Under-19 duty but scored his first international goal on the young Lions 1-1 draw with Switzerland and, although Pearson is pleased to see Mattock playing games, he would rather have him with the City squad.
He told the club's official website: "I would rather have him here to be honest but he is not.
"The tournaments are not always at the right time for us but on the other hand they are not always at the right time for them either.
"I would rather he was here preparing for the season but at least he is getting some pitch time.
"He is a fit lad and I'm sure when he comes back he will fit in no problem."