Mitrovic scored both goals as his country beat Nigeria 2-0 at Barnet's The Hive Stadium last night.
The striker joined Fulham on loan in January after a half-season on the fringes at Newcastle.
Mitrovic has scored seven goals for the promotion-chasing club, which is managed by his Serb countryman Slavisa Jokanovic.
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Krstajic spoke about Mitrovic's club future after the Nigeria game.
"Mitrovic was very lucky to be coached by Jokanovic, a coach from Serbia who knows him very well,” said Krstajic. "Mitrovic did a very good thing in choosing to come to Fulham.
"I’m sure that after the loan he will move to an even bigger, better club, where he can do much better.
“Personally, it’s a great pleasure to have a player such as Mitrovic in our squad. He’s a killer up front, which he proved (against Nigeria).”