With four goals and some show-stopping displays to his name, Messi is emerging as the player of the tournament, but van Gaal says that it would be dangerous to expend too much energy worrying about him.
"We are playing against Argentina," he told Tuesday's pre-match press conference in Sao Paulo.
"We're preparing a strategy for a team, not individual players, so I'll be ready for Argentina and their players.
"Messi has been elected the best player in the world. There's a reason for that. If you score so many goals, you have an added value.
"But on the most important stage, he hasn't always pulled it off. He's always found it difficult to do that at international level and he wants to change that at this tournament.
"We want to stop him, so that's going to be quite a challenge."
While two-time winners Argentina are bidding to reach their first final since 1990, Holland are aiming to appear in the deciding match for the second time in a row, having lost 1-0 to Spain in the 2010 final.
Both teams won all three of their group-phase matches before each pulling off a pair of narrow wins in the knockout stage, and van Gaal says that there is very little between them.
"I don't think there's a favourite," said the 62-year-old, who will take over as manager of English giants Manchester United after the tournament.
"In the semi-finals, the countries are at the same level. The results have reflected that in the quarter-finals and the last 16, so I'd say it'll be a 50-50 match.
"We'll need a bit of luck. The coin has to fall your way."