Celtic manager Ronny Deila has apologised to Dundee United counterpart Jackie McNamara for his handling of Gary Mackay-Steven's transfer.
The winger has agreed a summer move to the champions, but the Tannadice boss was upset by the Norwegian discussing the possibility of signing the 24-year-old this month.
"I just have to say sorry if I have offended him in any way," said Deila.
"It's not a rule I have heard about before, so I have to learn from this."
Prior to Mackay-Steven reaching a pre-contract agreement with Celtic, United started that it would require a bid of £250,000 for them to part with the player in January.
Asked again if Celtic would attempt to sign Mackay-Steven in the next fortnight, Deila replied: "We will see. We know we have him from the summer and it's not in our hands.
"Dundee United are doing well, too, and I understand that they want to keep their squad.
"I was at a smaller club in Norway and everyone wanted my players all the time, so I am used to this."
Shaun Maloney has been linked with a third spell at Celtic, but Deila was playing down a move for the 31-year-old midfielder, who rejected a move to Leicester City last week over personal terms.
"I don't think that's going to happen, but you never know in football," he said, although the manager did stress his desire to see more Scots in his team.
"We have to build up Scottish football," he continued. "Celtic is a big club in Scotland and players should go through Celtic before going further, or put Celtic in the position we want to be in Europe.
"They know the league and know what it's about to play for Celtic. These things matter when you sign them."
Following Saturday's win at Hamilton, Deila was quick to dampen speculation about Kris Commons moving on.
The playmaker, who is out of contract in the summer, was substituted late in the game before giving his boots to a supporter and applauding fans after full-time.
"I spoke to him, but not about throwing his boots in," said Delia, when asked again about the 31-year-old's future. "I am sure he will have enough money to buy new ones.
"It's the same situation, we are speaking together. We want him to stay here and he wants to stay and it's just about getting things right.
"It's important to talk together and that's what we are doing."