The Owls are looking to freshen up their playing staff for a second season in a fiercely-competitive Championship.
Their campaign has not got off to the best of starts - with three straight defeats leaving them pointless in the league and out of the Capital One Cup.
Mandaric concedes that they remain 'short' in key areas and hopes to address those issues before the close of the summer transfer window.
He is, however, also aware of the need to free up space in Dave Jones' squad and has indicated that a number of departures are on the cards.
Mandaric told the Sheffield Star: "We have not been at the level I think we should be at for a lot of reasons and the main one is injuries to first team players.
"We are (also) still short of two or three players that we are looking for.
"We are missing four or five players who are all quality. When we get those back, we will be a lot better.
"We are looking to get out three or four players by the end of the month.
"I'm not concerned. I think we'll turn things around. We will have a good, competitive team. We've just got to be patient with the injuries. Luck is not on our side.
"Let's stick together and believe we're going in the right direction. You can't judge the team two games into a season."