Dave Wahl has walked out on the Brighton Bears less than two weeks into the new season.
The 25-year-old has returned to his native Canada without explanation.
Director Romek Kriwald said: "The first I knew about it was on Tuesday when Dave left me a message on my phone telling me he was homeward bound back to Canada. I consider what Dave has done to be very unprofessional."
Wahl was left out of the side for last Sunday's game against London Leopards when new coach Nick Nurse opted to play Michael Brown instead as one of the two non-work permit players allowed in each game.
Brown is due to receive his British passport in the next few days and Wahl would then have become available on a permanent basis.
The 6ft 8in guard joined Bears last season and was one of only four players who returned when Nurse took over as coach and re-built a squad which has finished bottom of the southern conference for the last two years.
Kriwald added: "I know Dave was disappointed that he wasn't suited up for the Leopards game, but I spoke to him afterwards and he even said he would help me promote tonight's game against Derby.
"He was happy that the team had won on Sunday. I was always hopeful that we could get Dave back for this season, he was one of the players I wanted to return. He's always struck me as an intelligent guy and when we've had any issues in the past we've sat down and discussed them and sorted things out.
"To be honest I'm stunned. He was going to be an important part of the side and to walk out on the club like this is a real kick in the teeth for us."
Bears aim for a second successive home win when they take on northern conference strugglers Derby Storm at the Brighton Centre tonight (7pm).
It sees the return of Danny Hildreth who linked up with Storm last month after three seasons with Brighton.
He said: "I'm sure the fans appreciate why I had to leave and give me a good reception, whatever happens I'm looking forward to it."
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