Bobby Petta believes Celtic will be eager to vent their frustrations on Hearts tomorrow as the Parkhead side begin their defence of the William Hill Scottish Cup.

The curtain came down on the Hoops' European involvement this season when Neil Lennon's side meekly capitulated against AC Milan on Tuesday night.

While Petta expects that the true effect of exiting from Europe entirely will be felt keenly by the club for some time, he has maintained that the players themselves will want to return to action as soon as possible.

"Having been in that situation I personally always felt that another game couldn't come quickly enough," he said. "You want it out of your system as quickly as possible.

"After a game like that you are going over it and over it in your mind and the chance to get back on the pitch takes that away from you. I'm sure the Celtic boys will all be looking forward to the game at Tynecastle because it is a chance to put the memory of Tuesday night to bed."

Petta has also called upon Celtic to back Neil Lennon with funds in January and this summer.

The lack of a quality striker has been shown up this season and the Dutchman believes that if the team are to continue to make inroads in the Champions League then they need to spend a bit of money.

"It is really gutting that there is no European football, but the campaign has shown up the lack of quality within the squad. I don't think you can get away from that," he said.

"The hole that Gary Hooper left has never been filled and that is always going to come back to bite you when you are competing at this level.

"If you want to go forward and keep building then you have to spend a bit of money. Everyone knows that you can't go out and spend some of the sums that the club did in the past but there could still be a decent level of investment.

"This season seems like a surprise in the Champions League because the club have always performed so well in the competition. But it isn't all that surprising when you look at the squad because there are areas that definitely need to be strengthened and the Champions League was always going to show that up."

Lennon himself acknowledged after Tuesday night's game that the focus will quickly shift to gearing Celtic up to making another assault on the tournament next season, and, as such, thoughts of personnel will dominate his thinking in the latter stages of the campaign.

However, of more pressing note are the domestic demands of securing the title and defending the Scottish Cup.

While domestically there are few significant challenges for Celtic, it could mean that the remaining six months of the season lack a tension and sparkle that the appendage of Europe would have lent it.

Petta, though, has warned that while Hearts are a changed side these days, there will still be a charge in the air at Tynecastle when the teams meet tomorrow.

The last thing Celtic want to do is complete a disappointing week by being caught short in the Scottish Cup. Morton shocked them earlier this season in the League Cup and Petta reckons that there will be no repeat on this occasion.

"As a Celtic player I always felt that the games at Tynecastle against Hearts were second only to games at Ibrox," he said. "It is difficult to explain, but there was just something there.

"There was always a really big atmosphere and it's not just because the supporters are so close to the pitch. There was a real tension between both sets of fans and while Hearts are much weaker as a team now, that same feeling will still exist.

"The Hearts players will be well up for the game because they will think they have nothing to lose and they'll want to capitalise if Celtic are caught feeling sorry for themselves.

"Winning a League and Scottish Cup double is still a big achievement. Everyone would have loved the chance to still be in the Europa League or even the Champions League but it has gone now and the players need to be allowed to go out and enjoy the rest of the season.

"It might even be a chance for some of the younger players to bed themselves properly into the team and show what they can do.

"I've not spoken to Neil for a few weeks because I know how busy he is, but I know what he is like and he will be demanding a big performance."