Celtic manager Ronny Deila has hit out at Scottish Football Association disciplinary rules after Aleksandar Tonev's seven-match ban for racist language was upheld.

Tonev was described as neither a credible nor a reliable witness by an SFA-appointed judicial panel in a report that was published following the failure of his appeal.

The report revealed Aberdeen defender Shay Logan had accused Tonev of calling him a "black c***" during a Scottish Premiership match on September 13 and the panel found the on-loan Aston Villa winger guilty after describing the Dons player as an "impressive witness".

The SFA's disciplinary rules, like civil court cases, do not require that guilt be established beyond reasonable doubt, unlike criminal cases.

The criteria for finding Tonev guilty was summed up in the report as ''it is more likely than not that the subject of the complaint committed the act of misconduct alleged''.

But Deila feels more proof was needed - no one else heard the offending words, although Logan quickly told others.

The Norwegian said: "You can't judge a person on word against word, in my opinion. You will never do that in any real court.

"There is no proof and we still believe him. We will continue to do that when we don't have any other proof.

"You call another person a racist just on a word? I can't understand this happening.

"For me, if you are going to judge someone you have to do it with real proof and not word against word. Because a Bulgarian guy, with not very good English, is going to defend himself? Not so easy."

Celtic vowed to address issues raised in the proceedings with the SFA but there appears to be no recourse for challenging the decision again.

"I don't think there is any possibility to go further," Deila said.

"We have to take the penalty but we still feel it is not right and we believe Aleksandar in full."

Celtic have consistently stood by Tonev and there appears little chance of him being returned to Aston Villa midway through his season-long loan.

"He still has a future here," Deila said.

"Of course it is going to be difficult being seven games out but that's football. The most important thing is we stay behind him and support him.

"We are going to give him some days off to go to Bulgaria for Christmas and when he comes back he will be fighting to get back in the team.

"He is very disappointed of course but he moves on. He knows his innocence and he will just keep on going."

The damning nature of the report might make it difficult for Tonev when going to opposition grounds but Deila does not feel the player will be universally condemned.

"I think football fans are clever people as well," he said.

"They can see behind the case and behind the results as well. I say we have to have proof."

And he feels the 24-year-old will still want to play in Scotland.

"I think so but I haven't talked a lot about this," Deila said. "But he is training well for the two days and he seems good."

Celtic skipper Scott Brown reaffirmed his support for his team-mate.

"We all stick by him, we know what happened and stuff like that," Brown said.

"His training has been excellent, he has enjoyed training and there has been good banter with the lads as well.

"It's going to be hard, it's a long few games he is going to be out for but he will work in training, he will work on his fitness and when he's available he will be back in the squad.

"He has spoken to the players and we all stand by him."

There was more controversy in the SFA disciplinary procedures this week when Dundee United midfielder Paul Paton was banned for two games for spitting despite being publicly backed by his alleged victim, Aberdeen winger Jonny Hayes.

The suspension rules Paton out of an awkward meeting with Celtic on Sunday as he awaits the procurator fiscal to consider charges against him for an alleged assault on Celtic goalkeeper Lukasz Zaluska.

When asked about the issue, Deila said: "I don't think we will use any energy on that. We are looking forward to the game and this is outside the pitch.

"I was at Dundee last weekend and they are very, very nice people. There is a good culture at that club.

"Again, we don't have any proof about that. It's a football game and we are looking forward to it."

Meanwhile, Deila insisted there had been no approaches for Kris Commons or Virgil van Dijk but confirmed he had taken 22-year-old Everton midfielder Francisco Junior on trial this week.

The Guinea-born player was previously with Benfica and Manchester City and had a loan spell under Deila at Stromsgodset.

"He is a player I know from before," Deila said. "I haven't decided yet if he is going to stay for some more or he is going to go back."

Meanwhile, striker John Guidetti is fit for Celtic's Scottish Premiership contest with Dundee United on Sunday after overcoming the knee knock that forced him off against St Mirren.

James Forrest is also fine after going off with a migraine and Mikael Lustig could return to the squad following a hamstring injury.

Charlie Mulgrew (knee) and Jason Denayer (foot) remain out, while Aleksandar Tonev resumes his seven-match ban for racially abusing Aberdeen defender Shay Logan.

Provisional squad: Gordon, Fisher, Matthews, Izaguirre, Ambrose, Van Dijk, Johansen, Bitton, Brown, Forrest, Commons, Scepovic, Wakaso, McGregor, Griffiths, Guidetti, Stokes, Zaluska, O'Connell.