Mandaric will use the busy holiday programme to assess Gray's candidacy for the permanent manager's position and will not rush the process of appointing Dave Jones' successor.
Wednesday face Wigan, Bournemouth, Blackburn, Charlton and Blackpool between Wednesday evening and New Year's Day.
Owls chief Mandaric told The Star: "We are looking at everything and watching Stuart very carefully.
"His time is extended. We all have to get behind him and the team and give him full support and some space.
"It will be a good test of Stuart's ability, and I think he is a proper coach.
"It is more important to support him during the holiday period so we are not going to push very hard as far as interviewing goes."
Wednesday will be optimistic about their chances of beating Wigan at Hillsborough following a recent upturn in results, even though they still remain in the relegation zone.
After Wednesday upset high-flying Leicester 2-1, they then went down to a 1-0 home defeat by Nottingham Forest.
However, the Owls then downed Watford away from home on Saturday, with on-loan striker Connor Wickham continuing his good form.
New Latics boss Uwe Rosler is wary of the threat posed by the rejuvenated Owls but is confident of his side's chances if they focus on themselves and not on their opponents.
Wigan ended a run of six successive defeats in all competitions with a 3-2 derby triumph over Bolton in Rosler's first home match in charge.
The German was delighted with his team's showing in that match and hopes it will be the catalyst for better times to come.
"It was a derby game and we wanted to stop the rot and wanted to start to turn the momentum into a positive one, and the players dug deep," he said on Latics player.
"It was not an easy win, it was a very hard-fought win and I praised the players a lot and I'm still doing it because that was a massive turning point for us."
The former Brentford boss is now hoping for more of the same against third-bottom Wednesday, although he is not expecting it to be easy.
"Every game is different and they will ask different questions of us from Bolton. I think Sheffield Wednesday are a massive club," said Rosler, whose team moved level on 25 points with 13th-placed Watford with their derby triumph.
"(They have) big, big potential and they had been under-performing, but even when they had poor results that was not always the way they were playing.
"And now it looks like they've broken the deadlock, they are scoring more goals and picking up more wins. For us it will be a very very hard game."