The Inter Miami forward was Argentina's hero in Friday's win over Ecuador, scoring a 78th-minute free kick to get the world champions up and running with a 1-0 victory in their World Cup qualifying campaign.
However, Messi asked to be substituted in the 89th minute after he picked up a knock, and he subsequently underwent precautionary tests at a medical facility on Saturday.
Scaloni has revealed that a decision on Messi's involvement will be made on Monday, raising the possibility that Argentina's talisman may not be fit to start.
If Argentina decides to utilise Messi from the bench, experienced forward Angel Di Maria could be brought into the front three to feature alongside Nicolas Gonzalez and Lautaro Martinez, with the latter set to earn his 50th international cap.
There were also concerns that Cristian Romero sustained a minor injury in Friday's win in Buenos Aires, where his resolute defensive performance earned him the player of the match award.
However, the Tottenham Hotspur defender should be available for the trip to La Paz after being pictured in Argentina training.
With Manchester United's Lisandro Martinez struggling with a foot problem, Nicolas Otamendi is expected to retain his place in central defence alongside Romero, while the two full-back positions will be filled by Nahuel Molina and Nicolas Tagliafico.
Argentina's back four and Aston Villa goalkeeper Emiliano Martinez will be looking to help their country record a sixth consecutive clean sheet since beating France on penalties in the 2022 World Cup final.
There is unlikely to be any change in the middle of the park, with Liverpool summer signing Alexis Mac Allister set to work alongside Enzo Fernandez and Rodrigo De Paul.
Argentina possible starting lineup:
E. Martinez; Molina, Romero, Otamendi, Tagliafico; De Paul, Fernandez, Mac Allister; Di Maria, Gonzalez, La. Martinez