The Hornets made two offers for the midfielder earlier in the summer, the first around £1.2million before upping it to £2million, says the Watford Observer.
“Obviously, I was aware of it and knew it happened," he told the Daily Record.
“You never want players that want to leave your club, of course you don't.
“But it is not as black and white as the player wants to leave a club.
“There have been opportunities presented to him and he believes they are better for him.
“We know we have a really talented player on our hands.
“We know it is important that we nurture him in the right way.
“Until somebody comes along with a bid that the club finds acceptable he is going to play for us.
“In terms of handling it I spoke to Lewis about it, I spoke to him about it before it happened.
“I spoke to him while it was happening and I have spoken to him since.
“I have no doubts on Lewis' mentality.
“The reason he will be in demand is because he is a top player."