Besides Sykes and McGuiness, the band comprises of Max George, Siva Kaneshwaran and Tom Parker.
Sykes is recuperating from an operation that could prematurely end his career, but will never be without the band, reported Daily Star.
"He (Sykes) will always be part of the group whether he sings or not," McGuiness said.
The band members are concerned about Sykes but have an optimistic approach towards his treatment.
"There is always a bit of concern there. He is only young so chances are he will be fine. But there is that underlying worry because it was a huge operation," George said.