Since succeeding Ruben Amorim in January, Carrick has guided United to third place on the Premier League table.
Away with the Belgium squad this week, Lammens was asked about what Carrick has changed.
"From the very first day he made everything very clear and gave a straight message. He didn't make it too difficult or complicated for us," Lammens told The Athletic.
"Sometimes coaches make the plan too complicated. Then not all players buy into it and it will be difficult to get them all on the same level."
Instead, he highlights clarity under Carrick as a decisive factor.
"Right from the first game it was clear what he wanted. He did not require the most advanced, but made the players perform based on their strengths. First it's about holding tight at the back, then the offensive players can decide. That's what has worked best."
Another change highlighted is the team's defensive stability.
Carrick has moved to a four-back, which according to Lammens has provided better balance in the game.
"Michael has given us a lot of confidence and stability from behind."
The goalkeeper also highlighted Harry Maguire as an important influence.
"For example with Harry Maguire in front of me, he is also a monster, so it's always nice to have him there," he concluded.