Rebic joins Milan on the European transfer deadline, the Croatia international swapping the Bundesliga for Serie A on a two-year loan deal.
Rebic had been linked to Serie A rival Inter throughout the transfer window but the former Fiorentina forward – who arrived at Eintracht from La Viola on an initial loan deal in 2016 – returns to Italy via Milan.
He moved to Fiorentina from RNK Split in 2013 but struggled to make an impact before being loaned out to RB Leipzig and Hellas Verona.
Rebic eventually made his way to Eintracht, where he completed two successive loan spells before the German side made the deal permanent for around €2million at the end of 2017-18.
The 25 year-old, who was part of the Croatia team that reached the 2018 World Cup final, scored 10 goals across all competitions last season.
Rebic scored nine Bundesliga goals and supplied four assists alongside former star team-mates Luka Jovic and Sebastien Haller, who joined Real Madrid and West Ham respectively in the close season.
The trio played a key role in Eintracht's memorable run to the 2018-19 Europa League semi-finals, but Adi Hutter will be hoping Silva can help fill the void up front after agreeing a two-year temporary deal.
Silva arrived at Milan from Porto amid much fanfare in 2017 but the Portugal international spent last season on loan with Sevilla, scoring nine LaLiga goals and 11 across all competitions.
The 23 year-old arrives after new signing and fellow forward Bas Dost scored on his debut in Eintracht's 2-1 win over Fortuna Dusseldorf.