Speaking to the Scottish Sun, a police insider said there were "very real" fears that Loyalist marchers could represent at anti-independence protests.
They said: "We saw very serious disorder last year. This year Indyref2 tensions are added in the mix. It could inflame things at a time when we're stretched for resources."
Last year Police Scotland dealt with increasing numbers of large-scale protests on issues including independence, Brexit and climate change.
Deputy chief constable Will Kerr told the newspaper: "A dynamic political landscape presents the possibility of large-scale protests regarding everything from Brexit to independence and climate chage. All of these factors contribute to an operational environment in 2020 that will need the mass mobilisation of officers."
AN SNP spokesman said: "It would be very disappointing if there was a repeat of some of the violence that marred some marches last year."
A Scottish Conservative spokesman said: "The fact that senior SNP ministers casually use extreme nationalist language does not help."