So it's fair to say Frank Lampard and Cesc Fabregas didn't get along during their careers.
That year, the English midfielder informed: "I'd hate to put pressure on him. What I've done at Chelsea will never change.
"I hope they do well - Cesc and myself have had our battles in the past but I wish him the best because I wish Chelsea all the best."
Just how real was their rivalry, though? The same two players coming to blows twice a season isn't exactly normal but perhaps to be expected during such a heated Premier League fixture.
To take that loathing off the pitch takes things to a different level, though, and although they'll never be any definitive proof, Jack Wilshere didn't mince his words on Twitter in 2012.
The young Arsenal man posted: "I think Cesc would love to score tonight… him and Lampard never liked each other on the pitch," before Chelsea's Champions League semi-final with Barcelona.
Nevertheless, Lampard couldn't help alluding to the past tension between him and Fabregas during a brilliantly honest discussion with Martin Keown and Rio Ferdinand on BT Sport.
Lampard's Chelsea career looked doomed by the end of the 2012-13 campaign but an impressive goal scoring run only bought him another year under Jose Mourinho.
There were certainly some eyebrows raised when the Englishman's move to New York City FC came just days before Fabregas was then brought in.
And when the 39-year-old was mistakenly asked what it was like playing with Fabregas, he responded: "We never played together! They let me go to get Cesc in.
"Me and Cesc never really got on well on the pitch so they didn’t think we could share a dressing room."
It's unlikely that the Fabregas tension was the sole reason that Lampard was shepherded out of Stamford Bridge but it clearly played on the mind of those at Chelsea.
Nevertheless, the Spaniard would get the final laugh as he inspired the Blues to a fourth Premier League title with a deluge of assists in his debut campaign.
As the club's all-time top scorer and a bona fide club legend, though, we all know who Chelsea fans would rather have in their dream midfield.
Who would you rather have in your dream Chelsea midfield - Fabregas or Lampard? Have your say in the comments section below.