Argentina captain Messi missed Paris Saint-Germain's last two games with a knee injury after being substituted during the 2-1 win over Lyon. Messi was back in training on Monday and could feature in Tuesday's Champions League game against Manchester City.
His presence is a big boost for Scaloni. Messi, who lifted the Copa America with Argentina this summer, scored a hat-trick in Argentina's 3-0 win over Bolivia in a World Cup qualifier on Sept. 9. In doing so, he moved past Pele with 79 goals, two more than the Brazil legend, to become the all-time men's leading scorer in South American competition.
Aston Villa's Emiliano Martinez and Tottenham Hotspur pair Cristian Romero and Giovani Lo Celso are also on the list. Those players were at the center of a bizarre controversy that saw a September qualifying match at Brazil be halted and later postponed over quarantine rules.
Argentina take on Paraguay in Asuncion on Oct. 7 before hosting Uruguay in Buenos Aires three days later and then Peru on Oct. 14.
The Albiceleste are second in their group with 18 points from eight games and six points adrift of leaders Brazil.