The Saints had been tipped by many observers to struggle this season after a host of key players followed former boss Mauricio Pochettino out of the club.
"A lot of fans and a lot of the media were talking about a meltdown at the football club without really giving the club a chance to appoint a new manager and see which players he was going to sign and replace the ones that left," Le Tissier told talkSPORT.
"But Ronald Koeman has come in and done an absolutely superb job. He is very impressive, as a bloke and as a manager.
"The signings he has made have really hit the ground running."
Former Netherlands captain Koeman succeeded Pochettino as Saints boss in June.