This period in a FIFA World Cup™ year is always filled with nervous anticipation as the 32 qualified teams begin to make their final preparations. Coaches make surprise call-ups, tinker with their tactics and cast their eye over their squads - some for the final time - before deciding who will fill the 23 seats on the plane.

FIFA.com kept up a close eye on all the action across the globe this week and here are five things we learned from the March friendlies.

Some World Cup regulars were given food for thought The headline result from the week was undoubtedly the crushing 6-1 defeat of Argentina by 2010 World Cup champions Spain, but La Albiceleste were not alone in needing to reflect on an unexpected result. On Friday, France surrendered a two-goal lead in a 3-2 defeat to Colombia and, despite an encouraging victory against Egypt, Portugal were defeated 3-0 by the Netherlands.

Other tournament regulars also stuttered this week, mostly against teams not bound for Russia. Japan drew against Mali and were defeated by Ukraine, Australia were thumped 4-1 by Norway, Sweden lost to Romania and Chile, while Croatia were comfortably beaten by one of the week's outstanding Russia-bound sides: Peru.

Isco showed his credentials to one day be The Best The Real Madrid man truly stole the show with his hat-trick against Argentina. With Lionel Messi only able to watch on due to a minor hamstring complaint, Isco provided the star dust and proved his value to Julen Lopetegui. Playing to the left of Diego Costa, Isco scored three reasonably straightforward goals but it was his all-round performance that drew plenty of plaudits - playing a key role in the majority of Spain's attacks. Cristiano Ronaldo's crown may still firmly be on his head, with a late match-winning brace against Egypt on Friday demonstrating thus, but Isco this week certainly made it known that he could take over one day.

Defensive tinkering provides answers, and some questions England manager Gareth Southgate surprised many when he named both Kyle Walker and Kieran Trippier in the starting line-up for his side's friendly against the Netherlands. The Manchester City man has long been known as a flying full-back, but was positioned as the right-sided of three central defenders, with Trippier out on the right flank as wing-back. Not long into the game in Amsterdam, Southgate's selection began to make a lot of sense - Walker burst forwards several times, providing an extra option in midfield.

Walker was not the only defender in slightly unfamiliar territory this week, with Marcos Alonso featuring for Spain as the left-back in a back four, despite operating as a wing-back for Chelsea. France coach Didier Deschamps also tried Benjamin Pavard as his rather cautious right-back against Russia - Pavard regularly plays as a central defender for Bundesliga side Stuttgart.

Young forwards look set to fire at Russia Some of the world's top young strikers were given an opportunity to stake their claim for a World Cup berth this week, perhaps giving an early insight into the race for the adidas Golden Boot at Russia 2018. Gabriel Jesus proved the matchwinner for Brazil against Germany, while the Nationalmannschaft gave Timo Werner a chance to impress against Spain. Elsewhere, Kylian Mbappe grabbed an impressive brace for France against the 2018 hosts, while Breel Embolo's goal for Switzerland against Panama displayed his pace and finesse. These four - with an average age of under 21 - will certainly give some defenders sleepless nights ahead of the global finals' big kick-off.

Peru prove their worth A nation returning to the World Cup for the first time in almost four decades will usually be one whose expectations are reasonably low. However, La Blanquirroja supporters will be quietly encouraged by their outstanding performances this week. First, they comfortably defeated a strong Croatia side (including Ivan Rakitic, Luka Modric and Mario Mandzukic) 2-0 in Florida - despite playing the final 15 minutes with ten men. Then, they saw off Iceland 3-1 in New Jersey with another impressive performance. Los Incas fans will only want to whisper it, but Peru could be the surprise package at Russia 2018.