Dunn, 30, lasted only nine minutes on the opening day at Ewood Park before limping off with a groin strain.

Despite his absence Blackburn went on to record a 1-0 victory against Everton, thanks to Nikola Kalinic's 14th-minute goal.

Dunn looked to be over the injury problems that have blighted a promising career by scoring 10 goals from midfield last season.

Those concerns about his fitness were rekindled on Saturday, although Allardyce believes the medical report will be positive.

He said: "David has done everything possible this summer, playing in every single pre-season game and joining in every training session.

"He was our leading goalscorer last season and we have never seen him as fit as he is now.

"Then lo and behold he feels his groin in the first five or 10 minutes. We are so disappointed for him but we do not think it is too bad and he will be back soon."

Blackburn continued where they left off last season, when they recorded back-to-back victories against Arsenal and Aston Villa to finish 10th in the table.

They carried more of a cutting edge than Everton and should have gone ahead after two minutes.

Morten Gamst Pedersen's clever chip released Martin Olsson but with only goalkeeper Tim Howard to beat he hoisted his shot over the top.

Blackburn then took the lead in the 14th minute following a mistake from Howard. He raced out his goal to try to clear his lines but instead spilled the ball and Kalinic, who missed most of pre-season with a groin injury, was on hand to sweep it home.

Substitute Mame Biram Diouf and Steven Nzonzi both failed to take advantage of good chances and Everton came close to equalising in stoppage time.

Phil Jagielka thumped in a shot from 20 yards but goalkeeper Paul Robinson showed good positioning to block it.

Howard's place could now come under threat from Slovakia international Jan Mucha, who arrived in July from Polish club Legia Warsaw.

Mucha is anxious to show what he can do in England's top flight.

"I have no reason to be nervous," he said in an interview in his homeland. "I feel fine. I have been doing my best in training.

"We have big ambitions. The team has good quality. Some players have signed new contracts and the club is established. We want to battle for the Champions League or the Europa League."

Everton manager David Moyes refused to condemn Howard and said: "The goal changed things. It happens.

"It was costly, though, a deciding moment in the game, but Tim has been really good for us."

Allardyce expects Kalinic to make his mark in the top flight this season after scoring just two goals in his debut Barclays Premier League campaign following his £6million move from Hadjuk Split.

Allardyce said: "It was a great piece of ability by Kalinic and maybe overshadowed by Tim Howard's mistake.

"To capitalise on it fully with a really good swivel and finish was obviously why we bought him.

"It gives him huge confidence to score more goals in the Premier League. I think he will, providing we can give him the opportunity to do so."