“We haven’t been together for seven months and now getting together with lots of new faces it has been a challenge, but the guys have been magnificent,” said head coach Felipe Contepomi.
“They are training with a lot of intensity, we are very pleased with how they adapted.”
The former Leinster playmaker said that the difficulty in predicting the Lions’ line-up and approach to the game had simplified his approach.
“For us it is very good, because we needed to focus on us and what we want to do and how we want to do it,” he added.
“And then we expect the best of the best from the British Isles, we know all their players and we expect them to be playing hard.
“They miss some cohesion or maybe not because they are such top players they can click in one moment.”
Argentina are ranked fifth in the world and took three wins from their six matches in last year’s Rugby Championship.
The Lions will name their team at 14:00 BST.
Head coach Andy Farrell will be without Mallia’s Toulouse team-mate Blair Kinghorn, but is likely to ask several of his squad to, like Montoya, pull off a six-day turnaround from domestic finals.
The Leinster trio of Jamison Gibson-Park, Tadhg Furlong and Hugo Keenan all missed Leinster’s United Rugby Championship win over the Bulls on Saturday and will be given more time to recover from injuries.
After playing Argentina, the Lions will fly to Perth and take on the Western Force in their first tour game on 28 June.
