Paul Gustard's decision to join Harlequins has given Eddie Jones a headache he could have done without on the road to Japan.
England will tour South Africa with Gustard in tow next month, but following the three-Test series the defence coach will say his goodbyes and start a new life as head of rugby at Twickenham Stoop.
He is not the first member of Jones' backroom staff to leave for another job -- Rory Teague departed in 2017 after less than six months as skills coach -- however, he is undoubtedly the most high profile.
Gustard has been one of the constants of Jones' England and his defensive nous was pivotal in the run of success that included two Six Nations championships and series wins in Australia and Argentina.
Both men insisted on Monday that Gustard had accepted the Harlequins offer with the blessing of Jones and the Rugby Football Union (RFU) but where does the move leave England?
With the 2019 Rugby World Cup appearing on the horizon, Jones does not have time on his side as he seeks to find a replacement. Here are three potential candidates to fill the defensive void.
A former rugby league halfback or hooker with Wakefield and Castleford, Davis has made his name as a miserly defence coach since crossing codes to join Bath's backroom team in 2006.
In his time at the Rec, Bath conceded just 1.69 tries per match in the Aviva Premiership and developed a reputation as one of the most tight-fisted reguards in the league.
The club also lifted the Challenge Cup in 2008, and shipped nine tries in as many matches en route to glory.
After leaving Bath, Davis spent three years at Wasps -- who he helped back into the playoffs -- before heading to the Ospreys in 2016.
His arrival in Wales was trumpeted at the time and he has been able to tighten the Ospreys rearguard.
However, following a PRO14 semifinal appearance in 2017, the Welsh region have suffered a disappointing campaign this time around and missed out on Champions Cup qualification as they lost 35-17 at Ulster on Sunday.
If the RFU has any hope of smuggling Edwards across the Severn Bridge then it should have already sent a SWAT team to Wales.
Edwards' CV is littered with success from his time with Wasps and Wales, while he also acted as defence coach during the 2009 British & Irish Lions tour of South Africa.
Having helped Wasps to European and Premiership titles -- both as an assistant and head coach -- he linked up again with Warren Gatland when he became Wales coach in 2008.
The pair enjoyed immediate success at the Principality Stadium as they led their adopted country to a Grand Slam, the first of three Six Nations titles in six attempts.
Those Wales teams -- who also reached the semifinal of the 2011 World Cup -- were built on uncompromising defence and in the very image of Edwards.
He is contracted to the Welsh Rugby Union until after the 2019 World Cup, yet he was interviewed for the Harlequins job, suggesting that he is ready for a new challenge.
The RFU could well face competition for Edwards from his former club in rugby league, Wigan, after the Warriors announced that head coach Shaun Wane would leave at the end of the current Super Rugby season.
Could England return to Saracens for their next defence coach? Andy Farrell and Gustard were both plucked from the Allianz Park coaching production line, so Sanderson can expect to come under consideration.
Sanderson would not need to make wholesale changes were he to be parachuted into the England camp as he will be familiar with much of the plans put in place by Farrell and Gustard.
He has worked with Jones before, too. Having been forced into retirement at just 26, Sanderson was handed a coaching role by Saracens at a time when the current England coach was a consultant.
Jones subsequently took Sanderson with him when he returned to Australia for an ill-fated spell with the Queensland Reds in 2007. When he arrived back at the north London club for a season as director of rugby in 2008, his protege was still on the coaching staff.
Sanderson has blossomed as a coach at Saracens but he has admitted in the past that his relationship with Jones has not always been an easy one.
"He [Jones] is uncompromising. And I'm strong-willed and emotional. He properly pushes you, some people to breaking point. He hasn't broken me but I've been close to it," he told the Guardian in 2015.
"I like working hard but I'm not a workaholic. I like rugby but it's not my life. I think Eddie would say himself that he is a workaholic. He'd want the best out of you but his standards are incredibly high."