The 26-year-old is out of favour with the Hornets and recently took in a loan spell with the Owls.
He made seven appearances for the Championship club before returning to Vicarage Road in early January.
Wednesday would be willing to explore the option of bringing McGugan back into their plans, with Mandaric revealing that he is a top target.
He said: “Lewis is a good player. He’s on our target list.”
Stuart Gray is hoping that deals will be completed quickly, with his side looking to force their way into play-off contention.
He is looking for fresh faces to be added to his ranks prior to Saturday’s home date with Bolton Wanderers.
He told The Star: “Hopefully someone will come in. We need to strengthen.”
|Team||Total Att Assist||Total Scoring Att||Total Pass||Accurate Pass||Touches||Appearances||Mins Played|
|Lewis McGugan||Watford / Sheff Wed||10||22||398||331||553||13||921|
Wednesday have secured three successive wins in the second tier, and five in their last seven outings.
They are now just four points adrift of the top six and dreaming of a possible push for promotion back to the Premier League.