The news from Aberdeen of Clark Robertson's latest injury - he was on the verge of challenging for a first-team place after several months of recuperation from a serious knee problem - might prompt Derek McInnes, the Pittodrie manager, to regret his decision to allow young defender Joe Shaughnessy to depart on loan to Falkirk.

With Aberdeen preparing to face Celtic at Parkhead on Saturday, McInnes expressed his disappointment last night that Robertson, hurt while on Scotland under-21 duty during their 1-1 draw in Slovakia, will now be sidelined for up to six weeks.

The left-back, whose knee was operated on following an injury against Motherwell last October and who only returned to the first team for the game against St Johnstone at the tail end of last season, had been included in recent McInnes squads.

Aside from losing his services, Aberdeen are without captain Russell Anderson, in rehabilitation for the next six weeks following knee surgery and, with Shaughnessy elsewhere, defensive cover is now light.

"It's far from ideal," McInnes said. "I'm disappointed because Clark has worked hard to get fit. We were looking forward to getting him back and trying to force his way into the first team. It is quite an unusual injury because he was well into the game and he has been back training for seven or eight weeks with us.

"He had finished his rehab and to pick up another injury is really disappointing for the boy because he had worked really hard to get himself back into the reckoning. We were hopeful he would have come back from the under-21 games champing at the bit and ready to push himself back into a starting place."

McInnes disclosed that he had rejected a bid from Ross County to take Robertson on loan last month as he felt the youngster was on the verge of regaining his best form.

Midfielder Willo Flood, kept out of the side for Aberdeen's win over Partick Thistle before the international break, has been back in full training since Monday with no ill effects and is ready to go at Parkhead. "If we had risked him he could have made it worse and we didn't want to take that chance," said McInnes.