The defender was nominated for the Player of the Month award in the Championship.
The 25-year-old was among the nominees for the Championship Player of the Month award for March following a string of fine performances for the Owls. And while he would ultimately miss out to Burnley's Sam Vokes, Carvalhal has been full of praise for the centre-back.
"Tom is a machine, like a Swiss watch, in everything that he does," he told the Star. "What we like in defenders is don't commit many mistakes.
"Tom is one of the players who will make very few mistakes during a season. He is a player who also understands how we prepare our team to defend."
The former Leeds United stalwart has been instrumental in helping Wednesday keep a hugely impressive defensive record this term. Despite the Portuguese's philosophy seemingly favouring the players that are looking to get forward, only three teams in the entire division have conceded fewer goals than they have this term.
While the side have been consistently strong the whole campaign, it has been in recent weeks that things have really started to click from a defensive standpoint.
In their last seven games, they have conceded just two goals, which has helped them to four victories in a row and seen them move five points clear of the teams chasing a play-off spot.
And Carvalhal will be keen for Lees to maintain his reliability until the end of the season to ensure that they remain in the hunt for promotion.