Palace have been poor in opening months of the 2026/27 Premier League season under the guiding hand of new boss Pierre Sage with Mateta making just three top-flight starts.
His red card in the 2-0 weekend Premier League loss at Tottenham has heaped further pressure on Sage's position as he prepares for a suspension for the coming weeks.
The France international remains in a dispute with Palace over claims the final year of his contract is not valid amid a FIFA investigation into the matter.
Mateta joined Palace on an initial 18-month loan, before making the move permanent and signing a four-and-a-half-year deal - including an option to extend it by a further 12 months - back in January 2022.
Palace activated that option in 2024, meaning his present contract expires at the end of the current season.
However, this was disputed by Mateta's representatives in the summer, with United tracking the 29-year-old hitman, who has bagged double figures for goals in each of the last three Premier League seasons.
Talks on a £30M deal will start when the winter window opens - but reports from TEAMtalk claim former Palace boss Oliver Glasner wants a reunion at Nottingham Forest - as Liam Delap struggles for goals at the City Ground.