Footage, as you can see above, has been pored over and examined as people in Spain try to work out why the hand of the world's best player was ignored.
Handshake fallouts are second nature to Premier League fans, of course. In recent times we've had countless discussions based on the likes of Patrice Evra and Luis Suarez, Anton Ferdinand and John Terry, Wayne Bridge and John Terry to name just three (and one antagonist twice).
But in Spain this incident has been attracting plenty of attention, and Baena has spoken out on the club website to pin the blame on Messi. In quotes translated via Marca English, Baena says:
It's a matter I'd like to clear up and settle. Many media sources take it for granted that I refused to greet Messi, even though they were the visiting team, we were the home side, and it’s them who walk past and greet us.
You can clearly see that I offered him my hand, but when he ignored it, I wasn't sure if he didn't notice it or whether it was something else. I didn't give the matter a second thought, but it was him who didn't shake my hand.
Baena was subsequently booked in the game for a foul on Messi.
Barcelona won the game 4-0 thanks to a hat-trick from Pedro Rodriguez and a fourth from Cesc Fabregas.
They have won all five of their fixtures in La Liga this season, and sit top of the table by virtue of a superior goal difference to Atletico Madrid.