The Chilean was close to signing a new deal in December 2016 before he changed his mind.
He eventually left in a swap deal with Henrikh Mkhitaryan to join Manchester United in January 2018, with just six months left on his contract.
Alexis Sanchez agreed to a new Arsenal contract before staging a last minute U-turn
‘We had a deal,’ Law told Goal.
‘It was in December and we had been talking to his agent (Fernando Felicevich) throughout all of 2016, the whole year. We got to December, I flew to Santiago and we did the deal.
‘The player agreed to it on a phone call from Fernando’s office. Fernando and I shook hands and discussed how difficult the negotiation had been and we had the deal done.
‘The contract team drafted the new contract and sent it over to the lawyers representing Sanchez and in that space of time, while the documents were being proofed, he changed his mind for whatever reason.
‘We don’t know who got to the player, or why he changed his mind. But the bottom line was, he did.’