After consecutive transfer windows of being linked with the likes of Arsenal, Diame was eventually sold to Hull City in the summer to make room in the West Ham midfield - and on the wage bill - for former Cameroon captain Song.
Many West Ham fans were sad to see Diame leave to join Steve Bruce's side after two seasons of swashbuckling, powerful displays with a sprinkling of brilliant goals along the way.
Fans felt the Senegal man was regularly played out of position by Hammers manager Sam Allardyce and Diame agreed. On leaving he told the Daily Star: "I should have left West Ham a long time ago, as with them I wasn't permitted to play in central midfield. You lose your bearings when you get shunted around all the different positions."
But Allardyce, armed with an array of statistics, said Diame was simply not consistent enough to play in central midfield for the East Londoners.
Few argued as West Ham took their summer signings total to nine, including the loan capture of 27-year-old Song. And as the former Arsenal star sparkled in the Hammers' dazzling first half of the season, Diame's goalscoring exploits - which included a strike against West Ham for his new club - went largely ignored.
After netting four goals in consecutive games for Hull, Diame sustained a serious injury which curtailed his flying start but he is now back fit.
West Ham's season has gone from the sublime to the ridiculous, flying high in fourth at Christmas to relegation form since.
And Song's form, or lack of it, has been one of the fundamental reasons behind the club's slide to mid-table. In the 2-0 defeat at Manchester City last time out, Song was hauled off after yet another ineffectual display in the heart of the Hammers' midfield.
He failed to acknowledge his ongoing teammate or his manager and his future seemingly lies elsewhere with Inter Milan the latest club linked according to the Mirror.
So in hindsight were West Ham right to move Diame on for Song? Both players are the same age, Song has more composure and class but Diame has power and pace to burn and no lack of skill too.
Song is yet to score for the Irons while Diame managed 10 league and cup goals from 71 games in the claret and blue. Diame was often unplayable for the Hammers, much like Song at the start of the season and in truth both have suffered from inconsistency.
One thing is for sure, if the nephew of ex-Liverpool and West Ham defender Rigobert does leave this summer, West Ham will once again be back to square one looking to plug the void left by Diame's exit.