Brown has failed to bring in new signings to the KC Stadium.
Michael Owen, Marc-Antoine Fortune and Fraizer Campbell have all rejected moves to the club.
“Of course I’m frustrated because I wanted to get players in and you want them in as quickly as you possibly can so you can work with them,” Brown told the Hull Daily Mail.
“We need to be a bigger, better and stronger squad than last year.
“The first two weeks of our pre-season is all about fitness, but now we’re to the football stage of that six-week period and you want the players in who will be playing for you next season.”
