Farren's family have made a public appeal for funds to allow the 33-year-old undergo medical treatment that will give him a chance of surviving serious illness.
Former Derry City and Finn Harps player Mark Farren has been battling a life-threatening condition for six years after being diagnosed with a brain tumour that halted his football career.
Remarkably, the Donegal native made a comeback from that setback to become Derry's all-time top scorer in 2012 and then joined Glenavon in the Irish League before his problems returned.
To date, €32,000 has been raised as the football community has rallied behind Farren's need for treatment, with a significant financial boost from the two Irish internationals.
Everton full-back Seamus Coleman donated £5,000 yesterday, while McClean, who played with Farren during his time with the Candystripes, donated £1,000.