Argentina are looking to win their third world title and first since 1986 and Paris St Germain forward Messi will be expected to play a key role in their campaign.
"I see him as always... eager to enjoy the World Cup," Scaloni told reporters ahead of Wednesday's game.
"He knows how to play wearing this jersey. He's enjoying his teammates, training sessions, the stay and the whole process."
Argentina will be without midfielder Giovani Lo Celso (26) for the tournament in Qatar and Scaloni said it would be difficult to replace him.
"Football-wise there's no similar player in the team," Scaloni said. "But it'll depend on what each match requires."
Scaloni said Marcos Acuna will be assessed ahead of the game against the UAE as he is carrying a calf problem.
The friendly will be Argentina's last test before their World Cup opener against Saudi Arabia on November 22.
