Dusan Tadic produced a contender for one of the worst penalty misses of the season as Serbia drew 0-0 with Romania.
Poland and Italy go head to head, while Russia host Turkey in the Nations League on Sunday.
Jose Mourinho was on a scouting mission to see Sergej Milinkovic-Savic when he watched Serbia's win over Montenegro, Sky Sports News understands.
Jose Mourinho watched Serbia win, while Bernardo Silva helped Portugal to victory.
Manchester United midfielder Nemanja Matic has withdrawn from Serbia's squad
for their fixtures in Montenegro and Romania due to injury.
Portugal, without talisman Cristiano Ronaldo, beat Italy 1-0 in the UEFA Nations League on Monday, while Turkey stunned Sweden.
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