Gimenez joined Feyenoord in the summer of 2022 from Mexican side Cruz Azul and has impressed massively since his transfer. In 105 games for Feyenoord across all competitions, Gimenez has accounted for 65 goals and 12 assists.
23-year-old Gimenez won the Dutch Eredivisie, KNVB Cup, and Dutch Supercup in his two-and-a-half years at Feyenoord. He also reached the semi-finals of the UEFA Europa League with Feyenoord in 2023.
Gimenez called his departure from Rotterdam "very emotional."
"This will forever remain my first big club in Europe," said Gimenez in a statement on Feyenoord's website. "And Rotterdam the place I left my home in Mexico for. That alone makes this departure one with many emotions.
"I have intensely enjoyed my two-and-a-half years at this club as well as in this city. From the first moment I entered here, I have been embraced by the 'Legioen'. The love I received from them and all the people at the club, I will carry with me forever."
Milan reportedly pay a transfer fee of 35 million euros for the prolific striker who will sign a contract until the summer of 2029 in Northern Italy. The 32-time Mexican international will take over Alvaro Morata's spot after his departure for Turkish side Galatasaray.
Feyenoord's technical director Dennis te Kloese said Milan's bid was "simply too high to refuse", even in the middle of the season.
"You obviously don't want to lose key players at this point, with so much to play for," said Te Kloese. "We therefore held off the boat for as long as possible, but at a certain point you reach a point - or rather an amount - where it is simply no longer justifiable as a club to keep saying no and it can no longer be explained to the player either."
Manager Brian Priske admitted he'd have preferred to keep Gimenez around for longer during the team's press conference before the Klassieker against Ajax.
"It makes sense that Brian Priske would have preferred to keep 'Santi'," the director continued. "But we still have a big, strong group with numerous internationals and fortunately a few players are returning from injuries as well.
"In addition, despite it being very short notice, we are obviously also looking at what we can do these last days of the window to strengthen the selection."
It won't take long before Gimenez will meet his old team again - AC Milan drew Feyenoord in last week's Champions League draw and will play the Rotterdam side during the knock-out phase on February 12th and 18th.
"I look back on our beautiful achievements with pride, with the title and the celebrations in the city as absolute highlights," Gimenez continued. "It will be crazy to return here in just a week and a half in the colours of another club, but I will always look forward to seeing everyone at Feyenoord again."
