Arsenal picked up a 2-0 win over Athletic Club at San Mames on Tuesday.
The Gunners had a testing challenge against the La Liga outfit, but came on top.
Gabriel Martinelli and Leandro Trossard made the difference off the bench.
Trossard provided the assist for Martinelli to break the deadlock. It was vice-versa for the second goal. Trossard found the back of the net with the help of a deflection.
Martinelli was handed the man of the match for his brilliant counter-attacking goal after just 36 seconds on the pitch, but Cristhian Mosquera was equally good in defence.
The Spaniard was signed for just £13 million from Valencia over the summer, and he is proving a huge bargain with his sublime defensive performances alongside Gabriel.
He has seamlessly adapted to the right centre-back role. Against Athletic Club, Mosquera completed an impressive 75 out of 79 passes with an accuracy of 95 percent.
The 21-year-old had 95 touches. He won seven duels alongside six headed clearances. The centre-back was dribbled past twice, but managed to quickly regain possession.
Mosquera has been a terrific find for the Gunners. Speaking to TNT Sports, Jurrien Timber heaped praise on the Spaniard after his sublime defensive showing at San Mames.
Timber said: “He did amazing! He’s still so young, the way he comes in, it looks so easy for him – winning his duels & on the ball as well, it’s great to have him next to me & I think he’s got a bright future ahead as well.”
Arsenal host Manchester City in the Premier League on Sunday evening. Manager Mikel Arteta has a huge decision to make on whom to play alongside Gabriel in the heart of the defence.
William Saliba has recovered from his ankle issue and has not featured in the last two games. Mosquera’s form provides the manager with a potential selection headache this weekend.
Stats from Fotmob.com