Kabir Kohli posted on both Instagram and Twitter bidding farewell to the Ajax defender, which seemed to all but confirm the deal to Manchester.
He even reveals that he tried to convince the defender to stay in Holland but to no avail, and told the Man United supporters to 'take care of him' when he arrives at Old Trafford.
Kohli uploaded a photo on Instagram with the Argentinian centre-back, with the caption, "Farewell dinner", adding: "Man Utd fans - treat him well".
The chef also tweeted: "Despite my best attempts at trying to convince Lisandro Martinez to stay for another year at Ajax, unfortunately, it seems like he's off to Man Utd.
"Man Utd fans - take care of him. He's awesome!"
Man United originally had a £42million bid for the Ajax man rejected, but are now said to have met the Dutch club's £46m asking price.
Red Devils boss Erik ten Hag knows Martinez well following his time as Ajax boss before he left for Manchester this summer.
And the Dutchman was clearly keen to reunite with the versatile defender, who made 36 starts in all competitions under him last season.
The Argentine played a key role in the club's back-to-back Eredivisie title wins and he now moves to England hungry for more silverware.