The sixth seed was tied at 5-5 in the deciding set with her Greek opponent when her smash was called out by a line judge.
Replays showed the ball landed inside the sideline but umpire Marta Mrozinska refused to accept Pliskova's pleadings to overturn the call.
Sakkari won the game and then served out the match to win 3-6 6-3 7-5. Pliskova did not shake Mrozinska's hand and instead smashed her racket several times against the side of the umpire's chair, breaking the wood.
