The centre-back missed over two months of action for the Championship side.
The defender was sidelined for over two months before he made his return during the Owls' victory over play-off rivals Birmingham City earlier this month. And while he admitted that the time spent out of action annoyed him, he suggested that the team's success during that spell provided him with some comfort.
"From a personal perspective, I was frustrated not to be involved but I wasn't frustrated watching us win every week," he told the Star.
"I worked tirelessly with the physios at the club and went abroad for a bit to try and get as fit and as sharp as I could.
"I just had that motivation to get back in the team and and do what I can. It helped that the team were on a great run."
In his absence, Carlos Carvalhal's men managed to maintain their place in the promotion race, winning five and losing just two of their 11 Championship fixtures in that time.
Since the 25-year-old's return, Wednesday have won both of their games, with a 4-0 thrashing of Brentford following the narrow win over the Blues. And Lees has seemingly provided an explanation as to why he has been able to contribute to the recent results after suggesting that the injury has become something of an inspiration to him.
"Being out for a while just made me appreciate playing every week and not taking it for granted," he added to the Star.
While Lees was perhaps rusty in the victory over Gary Rowett's side, the clean sheet against the Bees suggests that he is starting to rediscover the form that made him a mainstay of Carvalhal's team before he sustained the injury in December.
And with the motivation to ensure that he takes every chance that comes his way, it appears that the centre-back will need no extra determination to help his side earn promotion to the top flight this season.