Rovers face their third away encounter in the space of seven days at Millwall tonight with just two confirmed centre-halves at Ferguson’s disposal in Andy Butler and Luke McCullough, who both had a difficult time in Saturday’s 4-0 drubbing at the Scot’s former club Peterborough.
Gary Mackenzie is still sidelined with injury and veteran Rob Jones is short of match sharpness ahead of tonight’s game at The Den.
Rovers’ susceptibility at set-pieces again flared up with another poor concession at Posh, with Ferguson mindful of his lack of bonafide central defensive options at present – with the squad, in his view, somewhat unbalanced.
Ferguson said: “I think we are short of defenders and you can see that. We’ve only got two centre-halves fit and we’ll have to see how Rob reacts after training and we’ve only got one right-back in Mitch (Lund).
“Aaron (Taylor-Sinclair) can play as a third centre-half and at left-back. But we’re unbalanced because we have a load of midfield players and attackers and just need to get the balance right.
“Of course, I want to assess all the players and give them the opportunity. But it’s up to me to challenge them every day and that’s what I will be doing.
“A job has got to be done, simple as that. You can either do it with the ones you have got or without them. That’s up to them.”
With a third away trip in a week to negotiate, training time at Cantley Park has been limited, with set-piece drills having taken pre-eminence.
Ferguson added: “I’ve just said, ‘go and head the ball and stop your man scoring a goal’. We need to show a desire to do that and in two games I have been here, we have lost two (goals) from set-pieces and five throughout the season.
“There are always areas to improve and that statistic is one that keeps happening.”
Nathan Tyson (dead leg) will be assessed before kick-off. Keshi Anderson is more likely to return at home to Colchester on Saturday. Young loanee James Horsfield has returned to parent club Manchester City.
Last six games: Millwall DLWWDW, Doncaster DWLLWL.
Referee: C Breakspear (Surrey).
Last time: Millwall 0 Doncaster 0; April 21, 2014; Championship.