Borthwick captained Saracens to their win over Northampton on Sunday
Saracens have apologised to European Rugby Cup (ERC) for Steve Borthwick's failure to attend Monday's Heineken Cup launch at Cardiff's Millennium Stadium.
Skipper Borthwick, 30, was the only missing representative from the coaches and captains of the 12 English, Welsh and Scottish clubs attending the event.
Borthwick was told by Saracens to miss the launch and attend a team bonding session at a beer festival in Munich.
The ERC could hit the Premiership club with a 5,000 Euro fine.
Sarries chief executive Edward Griffiths said: "The decision that Steve Borthwick should attend a pre-arranged squad function was entirely the club's decision, and nothing to do with Steve.
"Nobody can doubt the professionalism and commitment of perhaps the most professional and committed player in the country.
Our total commitment to this year's Heineken Cup competition is writ large across every billboard in London
Saracens chief executive Edward Griffiths
"The clash of dates was unfortunate but, at the eleventh hour, we rationally decided it was more important for our captain to take part in a long-arranged and highly significant squad event than to attend a press conference where he was not nominated to be formally interviewed and from which his non-attendance became the main story."
Saracens get their European campaign underway when they travel to Clermont Auvergne on 9 October and follow that up with a home game against Leinster a week later.
"Our total commitment to this year's Heineken Cup competition is writ large across every billboard in London promoting our match against Leinster at Wembley on 16 October," Griffiths added.
"It's unlikely any club has ever embarked on such a marketing campaign for a group fixture.
"We look forward to resolving this matter with ERC, and playing our full part in a successful competition."
The club found themselves in trouble with the authorities last season when a dispute between director of rugby Brendan Venter and the RFU led to the South African being banned from the Premiership play-off final.