Arsenal defender Kieran Tierney is expected to miss the rest of the season with a knee injury, dealing a blow to the club's hopes of securing Champions League football for next season.
The Scotland international, 24, who sustained the problem in training last week and missed Monday's 3-0 defeat at Crystal Palace, will go under the knife in the next few days.
"A specialist consultation took place on Tuesday, and as a result of further discussions with Kieran and our medical team, it has been decided that Kieran requires surgery to his (left) knee," the club said in a statement.
"This procedure will take place in London in the forthcoming days.
"Kieran's rehabilitation programme will start immediately after his surgery, at which stage a clearer understanding will be established on his recovery timescale. However, it is likely that Kieran will now miss the remainder of this season."
Tierney's injury means he is a doubt for Scotland's rearranged World Cup play-off semi-final against Ukraine, scheduled to take place in June.
The Gunners are also assessing Thomas Partey's fitness ahead of Saturday's visit of Brighton after the Ghana international limped off at Selhurst Park with a right thigh injury.
Right-back Takehiro Tomiyasu is due to return to training in the middle of this month following a long lay-off with a calf problem.
Arsenal's heavy defeat at Crystal Palace left them behind fourth-placed Tottenham on goal difference, but they have one game in hand over their London rivals.