Darren Bent insisted he had to leave Aston Villa after too many "slaps in the face".
Brighton defender Greg Halford has agreed to extend his loan deal from Nottingham Forest until the New Year.
Rangers have targeted 30-year-old Irishman Daly as they look to persuade free agents to pledge their future to the club when their transfer embargo ends on September 1, with Motherwell midfielder Nicky Law reportedly a target too.
But United are still trying to keep Daly beyond the end of his contract in the summer and other clubs have apparently expressed interest in the Tannadice captain, who scored 22 goals last season and has 12 this term.
McNamara told STV: "Jon has been a great player for Dundee United in his time here. I think it's credit to him that he's highly sought after and I'm not surprised, it's not just Rangers."
McNamara revealed he had spoken briefly with Daly about his future and agreed to reassess the situation at a later date.
But the former Celtic defender expects Daly and any other player to look after their own future first and foremost.
"It's down to the lad and what's best for him and his family," he said.
"If it is with us then great, if not then it is part and parcel of football, you just have to get on with it."
Meanwhile, McNamara has not written off Johnny Russell's prospects of playing in the William Hill Scottish Cup semi-finals despite his leg fracture.
The striker revealed he had fractured a fibula on Monday just as United were being paired with Celtic for a Hampden clash on April 13-14.
McNamara said: "I think it's a minimum of four weeks we are looking at. Hopefully he's still got an outside chance of making the semi-final."