The pair, aged 45 and 46, were detained by detectives from the PSNI's Serious Crime Branch in Coleraine, Co Derry, this morning.
Mr McDaid was beaten to death outside his home in the Heights area of the town by a loyalist mob who had entered a mainly Catholic housing estate after Rangers beat rivals Celtic to the Scottish Premier League title.
Following the attack, the McDaid family lodged an official complaint with the independent Police Ombudsman office claiming the PSNI did not do enough to prevent the attacks.
The community worker's widow, Evelyn, was also injured in the attacks and sustained extensive head wounds.
