Champions League: 1st leg, Round of 16 - Arsenal FC vs FC Barcelona, Juventus FC vs FC Bayern Munich – Five things we learned

New Delhi: The European Champions League on Tuesday witnessed the continent's two top matches in the first leg Round of 16 battle. After the performance on Tuesday night, all four teams find themselves in contrasting positions ahead of the return leg three weeks later.

Arsenal, who defied Barcelona for over 70 minutes at the Emirates, paid for two costly mistakes in the end for Lionel Messi to stamp his authority and draw first blood. On the other hand, Pep Guardiola's Bayern Munich saw a 2-goal cushion slip, as hosts Juventus came back in lively fashion to get a crucial 2-2 draw at the Juventus Stadium in Turin.

With all these big sides battling for glory, here are five things we learned from the two big-profile encounters.

Juventus humbled in first half: The Old Lady of Turin weren't in the encounter in the first half to mention they were working hard chasing shadows. Bayern's wave of attacks kept coming in and the hosts managed to camp in their own half and just stick it out. But it wasn't too long when Bayern's wing-men displayed a moment of brilliance from Arjen Robben and Douglas Costa laying the ball for an easy finish through Thomas Muller.

Allegri's super-subs decision pays dividends: With 2-0 down and an hour gone, Juve seemed all done and dusted but manager Massimilano Allegri changed his tactics and injected more energy through three of his substitutions and the move paid off. The hosts capitalised on breaching the Bayern defence twice and made sure the chances were taken as a make-shift defence slept off at moments.

MSN trio make the difference once again: Barcelona's world class trio of Lionel Messi, Luis Suarez and Neymar pulled the trigger at the right moment waiting to break free on the counter. Barca broke the deadlock in the 71st minute through Messi after a swift counter-attack involving Neymar and Suarez. Suarez also hit the post as Neymar was denied by Petr Cech to highlight their involvement.

When will Flamini learn?: Arsene Wenger sent midfielder Mathieu Flamini when his side was trailing 1-0 and the Frenchman's first involvement even before touching the ball was a mistimed horrifying tackle on Lionel Messi inside the box to award the visitors a penalty. Flamini has been guilty many a times for reckless challenges and in a crucial UCL game this was a heartbreak.

Arsenal showed character before surrender: Arsenal deserve credit for the entire first half limiting Barca to 0 shots on target. The defenders alongside Olivier Giroud and Aaron Ramsey threw themselves in crucial challenges to keep Barca at bay for 70 minutes. With the onus on throwing more bodies upfront in search of a goal, Arsenal then paid heavily with gaping holes in the defence.