Watford's assistant manager Craig Shakespeare has has been speaking about playing without fans.
"Everyone keeps using the word 'strange' but I think the biggest thing for me is, without the fans, it's been slower," he said.
"There's a slower tempo. There's not the emotion of a tackle that gets the crowd going or a ball in the box. I've noticed such a slower tempo. You've noticed in a lot of games there's not as many goals."