Messi is still waiting on his first senior international honour, despite claiming five Ballons d'Or and four Champions Leagues in an astounding career.
The 30-year-old's failure to win a World Cup has so far counted against him in debates ranking the greatest players of all time, but Otamendi says Argentina's 25-year trophy drought – which stretches back to the 1993 Copa America – is not for a want of trying from their talisman, a four-time loser in international finals.
"In Argentina, we are very demanding, but we are lucky to have Leo - he helps a lot. He is always calm, he tries to deliver for the team. He's a competitor, a winner, in games and in training.
"Sometimes the game doesn't go as planned but he always looks for the best for the team. We try to help him, to give him what he needs, to make it work and take advantage of having him in the team.
"Given the players that Argentina have, [winning the World Cup] is a demand that we all want, but we won't win it in the first game. We will play each game like a final and destiny will tell us where we will end up.
"In Brazil, we got to the final and we almost won it, but it wasn't to be. We've had three finals where we couldn't do it, but if we get into that position again it's because the team deserves it.
"In Argentina, [Messi] is valued highly - there are comparisons with [Diego] Maradona. I am lucky to share a team with Leo and he wants to win a title with his country more than anyone."
12,5% - Argentina have only won 12,5% of South American 2018 World Cup Qualifying games without Leo Messi compared to 60% when he has played. Dependence pic.twitter.com/47V8C8H6cc— OptaJose (@OptaJose) March 27, 2018
"At a personal level, I'm having a very good season," he said. "I've adapted to the team, the play, Pep's ideas.
"I'm happy because I'm playing football how I've always liked to play it."