The two clubs have done plenty of business over the past decade, but the Rossoneri have not always come out of it too well
Diego Lopez was unveiled as an AC Milan player on Wednesday, signing on the dotted line to complete his switch from Real Madrid.
The transfer brings to an end a rollercoaster 18 months at the Santiago Bernabeu for the 32-year-old, with the constant politicking behind the scenes for Iker Casillas to regain his spot as number one being a thorn in the former Sevilla goalkeeper's side.
Lopez retained his composure throughout, becoming the first-choice keeper under both Jose Mourinho and Carlo Ancelotti to make 62 appearances in his second spell with Madrid.
However, the arrival of Keylor Navas and the expectation of more game time for Casillas led to Lopez being allowed to leave for Milan, with the Rossoneri moving quickly to add to their goalkeeping options. While they have already brought in Michele Agazzi from Chievo this summer, coach Filippo Inzaghi made it known that he felt the need to strengthen the position further.
Lopez joins a long line of players to move between Madrid and Milan of late, with some having far more success than others...
Ronaldo's was the first switch between the two sides in seven years when he called time on his spell at the Bernabeu to join Milan in a €7.5 million move in January 2007. The ace frontman brought with him one of the game's greatest repuations but also a huge burden of expectation for an ageing, injury-laden former force.
Having netted 104 goals in 177 games for Madrid, O Fenomeno was unable to replicate such form with Milan. He scored only nine times under Ancelotti, with a serious injury to his left knee sustained against Livorno in February 2008 hastening his exit from the club after only 20 appearances.
Milan hoped for better luck from the transfer which brought another Brazilian, Emerson, in from the Bernabeu in the summer of 2007. Having already won a Serie A title with Roma in 2001, it was hoped that the durable midfielder would quickly fit into Italian football once more.
However, things didn't quite go to plan, with the European champions beginning to fall by the wayside amidst the weight of old, heavy legs, and Emerson's story was endemic of the decline that was to come in the years to come. After just 27 appearances in two seasons, it was agreed by all parties to terminate the 33-year-old's contract in April 2009.
One player who bucked the trend of swapping Spain for San Siro was Kaka. The Curva Sud hero was sold by Silvio Berlusconi for a near-world record return of €65m in 2009 after turning down the €120m advances of Manchester City five months earlier.
But it was to be another transfer which never quite materialised as many had hoped, with injuries helping to hamper the Sao Paulo product's progress, while the change of surroundings also seemed to have an effect on a player who had become an idol at Milan thanks to his form over a period of years.
In the same summer that Kaka went one way, Klaas-Jan Huntelaar went the other, joining Milan in a €15m deal. But the Dutchman's performances couldn't earn him a regular starting spot and within a year he would be gone.
Huntelaar struck just seven times in 30 appearances in the red and black shirt, often finding Marco Borriello blocking his path to the No.9 slot in Leonardo's first team alongside Ronaldinho.
Four years after Kaka had made his high-profile move to Madrid, he was back in Italy. The Blancos cut their losses on the Brazilian, allowing him to return to Milanello on a free transfer.
But while Kaka was one of Milan's better players in 2013-14, the club's continued decline saw them miss out on European football and he would sign for Orlando City at the end of the season, with a loan spell at Sao Paulo being arranged to fill his time.
So Diego Lopez follows a mixed bag of signings in making the move between the Spanish capital and Lombardy, and the goalkeeper will be looking to be an improvement compared to the most recent examples.
When he takes to the pitch for the first time in a Milan shirt against Lazio on August 31, he will have the weight of history hanging on his shoulders.