The Argentine star floored James Milner with a brilliant nutmeg, producing a far more spectacular response from the former Barcelona boss.

Former Barcelona boss Pep Guardiola was in attendance for the Catalan giants' Champions League round of 16 second leg clash with defending English Premier League champions Manchester City.

The Spanish tactician watched on as the Blaugrana clinched a 1-0 victory over the Citizens, at Camp Nou, progressing to the quarter-finals on a 3-1 aggregate.

It is understandable to see the Bayern Munich boss, who enjoyed a wonderful spell at Barcelona as a player, still hold affection for the club, and its star player Lionel Messi close to his heart.

This was on show for the whole world after Guardiola was spotted hilariously reacting to some excellent footwork by the Argentine superstar.

Credited as being the man behind Messi's rise to stardom, Josep could not hold back the emotions as La Pulga pulled of an outstanding nutmeg on Manchester City's James Milner.

Dragging the ball between his legs before dashing off after the Englishman fell to the ground, “The Philosopher” was left amazed by Leo's skills and was caught on camera rubbing his face in shock.

Check out Pep's reaction below.

Messi nutmegging James Milner in Barca 1-0 Man City

Lionel Messi, James Milner, Barcelona, Manchester City, UEFA Champions League

Guardiola's reaction

Pep Guardiola, Lionel Messi, James Milner, Barcelona, Manchester City, UEFA Champions League

With Bayern Munich also through to the last 8, the possibility of Guardiola facing off against his ex-club in the European tournament remains a possibility. 

It would be interesting to see how the Spaniard fares against the team he won every possible accolade with if paired against each other.