Flanagan has been sidelined since the end of the 2013-14 season through a long-term knee injury.
The Frenchman has made an immediate impression in pre-season, and Cresswell is anticipating having to share one duty with him next season.
Gueye signed for Aston Villa, although Southampton were also interested in him.
After leaving Tottenham Hotspur this summer, the German midfielder will be looking to improve on his record during a recent loan spell.
Here is how Leeds will line up in their pre-season friendly against the Bundesliga outfit.
The 21-year-old Frenchman joins Villa after a stellar season at Nice, where his compatriot also played before spells at Monaco, Manchester United and Juventus, respectively.
The Newcastle midfielder is targeting Premier League progression.
Tottenham Hotspur have sold a player after just a year at the club, but did he deserve more time?
The Gers have now signed three Wigan players this summer, and both former teammate Don Cowie and Alex Rae think it's good business by the Glasgow club.
Leeds United are undergoing their first pre-season with Uwe Rosler as head coach.
Manchester City take on Manchester United this weekend in the Premier League, but which club's centre-back has made the better start in England?
Manchester City and Manchester United go head-to-head on Sunday and Louis van Gaal's side could cause something of an upset at the Etihad.
Manchester City signing Eliaquim Mangala has struggled so far.