Manchester United coach Mike Phelan joked that he couldn't handle another Rooney when Wayne's son Kai signed for the club.
The 11-year-old penned a deal in December which sets him on the path to follow in his father's footsteps.
Wayne is United's all-time leading scorer having spent 13 years at Old Trafford, several of them with Phelan as coach.
But the current United No 2 couldn't resist having a little fun on social media.
"Not sure I can handle another. Keep grafting young un and listen to yer Dad," he said.
Wayne and his wife Coleen took to social media to express their delight at their son's achievement.
The current Derby boss said at the time: "Proud day. Kai signing for Man Utd. Keep up the hard work son."
While Kai's mother said on Instagram : "Special night..... congratulations Kai. I love you and I am so proud of you.
"Keep trying your best."
Kai was pictured holding up a United shirt with the No 10 on the back - the same number his father wore.
In total Wayne scored 253 goals in 559 appearances for the Red Devils having moved from Everton as a teenager in 2004.
He won 12 major trophies at United including five Premier League titles and the Champions League.
Since then Wayne has returned to Everton, moved to the MLS and has since returned to Derby where he originally took up a player coach role.
The sacking of Philip Cocu back in November saw the 35-year-old assume the role on an interim basis before being appointed permanently - he currently has the Rams four points clear of the drop zone.
Kai is the oldest of the Rooney children, with the couple having three more sons - Klay, Kit and Cass.
