Aberdeen's hopes of getting some late scouting were scuppered when Sporting's scheduled domestic fixture against Gil Vicente was called off because of the outbreak.

McInnes, though, is focused on Aberdeen striking the needed balance as they look to progress to the play-off round and produce a swift response from Saturday's disappointing 3-0 home defeat by Motherwell.

"We have not really considered their problems too much," said McInnes, who is fully expecting the European fixture to go ahead – with a final decision from UEFA and the local public health authorities set for Thursday.

"We know their preparations have not been ideal, but if you delve into their squad and the quality they have to chose from, it is a formidable task, there is no doubt about it.

"But the excitement of being here and taking on such an opponent is why we work so hard to get into Europe every year.

"We have come across a tough one early on at this stage, but we are looking forward to the challenge."

McInnes added: "Your preparation has to be a lot on the opposition, but it also has to be on ourselves, trying to make sure we get the balance right to have the chance to land some blows on them.

"We are going to have to do a lot of things right in the game, defend well, have a good level of concentration and confidence in possession.

"A lot of these things are going to have to be valid tomorrow for us to get the result."

Aberdeen confirmed McKenna's transfer was for a club-record fee, believed to be around £3million.

McKenna, 23, came through the Dons' youth ranks, making more than 100 appearances and McInnes is confident the defender can go on to further his career in England.

"We are absolutely delighted for Scott," the Aberdeen manager said.

"While it was not ideal preparation (for Motherwell) with the disruption with whether he was going or not, what we have to look back on as a youngster coming through, he did everything right and was a really popular boy with every member of staff.

"He did not cut any corners and he is an example to a lot of youngsters when they come through – some think they are ahead of the game from where they actually are.

"Scott has done the yards and knuckled down, dealt with highs and lows, been pushed forwards into the national team at a young age.

"I hold him such high regard, we all do and we will miss him. He will go and do well there, he is ready for what is expected of him at Nottingham Forest."