The Newcastle boss is frustrated that his side will start the season with the transfer window open.
The youngster has joined Manchester City this summer.
Leeds United have two friendlies coming up in the next two days.
The defender joined Newcastle from Blackburn Rovers on Thursday.
Big things are expected of the diminutive attacking midfielder at White Hart Lane.
Pierluigi Gollini is one of three signings that Aston Villa have made so far this summer.
The Hoops have so far signed just one player, but Johnstone expects them to be busy in the coming weeks.
Tottenham Hotspur have confirmed their travelling squad to Australia.
The Basque coach was linked with moves to Nottingham Forest and Wolverhampton Wanderers before landing the Spain job.
Newcastle United drew 2-2 with Doncaster Rovers in a pre-season friendly on Wednesday.