I am curious why this tactic needs to be stopped? Is it happening every combat? Is it something that breaks a story element?
If it is something that has happened once, applaud the player for the creative thinking. Let the player begin to use it as a crutch. Once it becomes a standard tactic, knowledgable NPC's may learn of it. Have the fighter ready an action, then when the Wizard teleports in, have the fighter move away, 20' or 30', depending on movement. The Wizard will be forced to adjust tactics immediately. And it will be quite likely that the wizard will be in a bad position at that point.
Or, have the fighter surrounded by some allies. The Wizard is forced to teleport further away. Or, have the fighter's invisible rogue ally watching his back for sneaky wizard tactics. Wizard teleports in and takes a big sneak attack hit.
Of course, I am assuming that this is a DM question to counter a Player ploy, not vice versa. As a DM, I try to encourage my players to use cool, sneaky tactics. Sometimes, they come up with things that defeat the challenge quicker than I anticipated. Personally, I like that! So long as they don't try to totally abuse it, I let it slide. There are plenty of times when the challenge I put before them turns out to be tougher than I anticipated as well. But, this starts to get into DM philosophy, not answering your question.

Sorry about that.