Ronny Deila believes the pressure is on Aberdeen ahead of tomorrow's Scottish Premiership clash with Celtic at Parkhead.
The Hoops, who exited the Europa League on Thursday night on a 4-3 aggregate defeat to Inter Milan after a 1-0 loss in the San Siro, are three points clear of Derek McInnes' side with a game in hand as the title race resumes.
Celtic have already beaten the Dons twice this season and Deila insists a third victory would strike a mortal blow to the Pittodrie men's championship hopes.
"In my opinion this is the most important game we have had so far this season," said the Norwegian.
"The league is everything. It is going to be hard to reach us if we win.
"The pressure is on both teams but Aberdeen has to win, maybe a draw, to stay in the fight for the championship so this is a very important game.
"If we win we will put ourselves in a very good position.
"And with the progress we are making I would be very disappointed if we lost the points we were ahead.
"But again we have to win, and it is going to be tough.
"They are a very good team, with speed, good on the counter attacks, they have played together for a long time, they have consistency.
"You can see they have built from where they were so we have to put in a very good performance."
Deila was still shrugging off the disappointment of losing 1-0 to Inter but stressed he was not blaming referee Ivan Kruzliak, who sent off Parkhead defender Virgil van Dijk in the first-half for two bookings.
It was an uphill task for the visitors thereafter and in the 88th minute Fredy Guarin fired in a wonderful strike to cap a frustrating evening.
The former Stromsgodset boss believes that the Slovakian official was guilty of nothing more than a bad day at the office.
He said: "We have bad days, the refs have bad days. I don't think he will be very happy with his performance.
"But you can go back seven years or whatever, since I have been the manager, and see how many times I have blamed the referee. I think you will find it was zero.
"Yesterday was special. There were so many things happening and anyone can see that.
"But I am not blaming him. Everyone can have a bad day at work.
"When you get a sending off against a good team like Inter Milan, you know it is going to change the game.
"We had the game where we wanted it and these two free-kicks, they were free-kicks maybe but not a red card.
"But we have to move on and I hope that isn't the feeling (blaming the referee). That is wrong."
Celtic skipper Scott Brown agreed with the manager's assessment of the referee, saying "everyone has a bad day now and then" but also questioned what merits a yellow card in the modern game.
He said: "Everyone has a bad day now and then. I think if you pull out of every single challenge it's not really football.
"Football is a man's game there's always going to be tackles that are a wee bit late due to the pace of the game.
"These things happen but every single tackle shouldn't be a yellow card."