Apart from Cesc magnificent performance, I couldn't help but notice Sergi Roberto is a great partner to play alongside Cesc. Roberto has great workrate to cover for Cesc and allow him the freedom up front to do his game.
They are so complementary together because they play the inverse to the Xavi/Iniesta pairing. With a trio of Busi, Iniesta and Xavi, Xavi plays on the right deep, while Iniesta plays on the left forward.
Now with a trio of Busi, Cesc and Roberto, Roberto can play deeper, but on the left, while Cesc plays the forward role, but on the right.
Roberto obviously does not have the game control of Xavi, however he has massive workrate, is no slouch on the ball, and has projection. The Cesc/Roberto pairing can be more defensive and more direct on attack.