During their first stint as team-mates back in the late 2000s, the battle between Rossi and Jorge Lorenzo was so intense it was billed as a feud.
Such was the bitter rivalry that it played a role in Rossi swapping Yamaha for Ducati.
And although the relationship has been on friendly terms since the duo partnered up again in 2013, the result of Sunday's Catalunya MotoGP could reignite tensions.
Finishing first and second at the Spanish track with Lorenzo ahead of the chasing Rossi, just one point now separates the team-mates at the top of the riders' standings.
Added to that, Rossi reckons he was a match for Lorenzo in Sunday's race but was, once again, undone by his lowly grid position.
"I hoped to catch Lorenzo, but it was difficult," said the Italian.
"Unfortunately starting from the third row I lost a lot even though I was strong in the first lap. After this I was always there.
"I am happy as I had a good pace, good setting; my speed is equal in the race today to Jorge that is a good target."
He added: "After seven races we have one point difference and a similar pace, so it will be interesting I think!"