Steve Round has reportedly snubbed the chance to join Newcastle.
McClaren, 54, became Newcastle manager earlier this month, replacing John Carver in the St. James' Park dugout having left Derby County at the end of the 2014/15 season.
Now, McClaren is charged with the task of revitalising a Newcastle side which only narrowly avoided relegation from the Premier League on the final day of the campaign.
Signing new players will obviously be a huge part of McClaren's rebuild, but he must also look to assemble a coaching staff around him ahead of the new season - but that could be more problematic than first feared.
According to the Daily Mail, former Manchester United assistant manager Round has spurned the opportunity to work with McClaren again.
Round, 44, worked with McClaren at Middlesbrough and with the England national team, before re-joining McClaren at Derby County this past season.
It's now reported by the Daily Mail that Round was offered the opportunity to reunite with McClaren once again, but has rejected it - because he wants to become a manager himself.
Another rejection - problems for McClaren?
As well as this revelation about Round, McClaren has reportedly seen a number of other potential candidates reject the role too.
The Daily Mirror recently suggested that Bolo Zenden and Phil Neville also rejected the position, leaving McClaren without an assistant ahead of pre-season.
Newcastle and McClaren must solve this situation sooner rather than later, and whilst some may worry that Newcastle just aren't a big enough lure anymore, McClaren will stilll have a number of targets in mind 0- and will eventually find his assistant.