Romero has been a regular for his country in the past, but will enter the tournament short on competitive football.
The 27-year-old has made just four appearances for Monaco this season, none of which have come in Ligue 1.
But, despite that, Sabella says the former AZ and Sampdoria man will be his goalkeeper in Brazil, ahead of the likes of Mariano Andujar and Agustin Orion.
"Romero had a good match and I consider him an excellent goalkeeper who unfortunately is not getting continuity at his club," Sabella told Radio La Red.
"Apart from the odd injury he has always been in my team ... the position (at the World Cup) is his."
Argentina will take on Bosnia-Herzegovina, Iran and Nigeria in Group F at this year's World Cup.
Alexia Putellas: "We’re already the only club to have won the men’s and women’s Champions League, so the only thing even more historic to do than that would be to win it in the same season"
‘Trent has won everything he can for Liverpool, but of those who’ve left that we wanted to stay, who’s actually done better? I can only come up with one’: Reds legend highlights potential danger of Alexander-Arnold moving to Real Madrid
