Super Martinelli, contrasting Kepa & Leno ... Things learnt from London derby

In the 200th meeting between the two great London rivals, two of the youngest managers in the Premier League went head to head and the game didn't disappoint, as they played out an entertaining 2-2 draw to share the spoils at Stamford Bridge.

Both teams began the game energetically but Arsenal's defence came back to haunt them once again, as Shkodran Mustafi's calamitous back pass was latched onto by Tammy Abraham. 

The Englishman was clean through on goal and with the goal gaping, he was brought down inside the penalty area by David Luiz, who received his marching orders for a professional foul.

Jorginho calmly converted the resulting spot-kick to break the deadlock and although Arsenal pilled on the pressure despite being a man and a goal down, Chelsea went into the interval with their lead still intact. 

Despite the circumstances, the Gunners struck back in the second half in stunning style, as Gabriel Martinelli capitalized on Ngolo Kante's slip on the halfway line and finished emphatically after running the length of the pitch.

The second half produced some of the most exciting bits of football in the Premier League this year, as Cesar Azpilicueta scored what looked like a winner, as Arsenal once again failed to clear their lines defensively.

While the Blues looked like they were going to get the better of their London rivals once again, the Gunners dug deep and found a solution once again, as Hector Bellerin's fierce left-footed drive from the edge of the area found its way into the back of the net to restore parity for the away side.

As the two sides shared the spoils in what was one of the most entertaining and evenly matched London derbies in recent times, let's look at 3 talking points from the game.

Both sides have deep-rooted defensive problems

Arsenal's defensive frailties were compounded in the first half, as Mustafi's careless back pass led to Luiz taking one for the team and committing a professional foul. The Gunners have been shaky at the back for quite a while now and their defensive deficiencies were brought to the forefront once again.

Chelsea themselves have not been tight enough at the back this season and they were made to pay for their shortcomings, as Arsenal rallied back twice in the second half despite being a man down to secure a well-deserved point. 

While the likes of Luiz, Mustafi had torrid outings, Andreas Christensen and Antonio Rudiger were simply not good enough on the day and things have gone from bad to worse for Chelsea goalkeeper Kepa Arrizabalaga, who has been far from his best this season.

Both sides simply do not have the personnel to be resolute enough defensively and they need a massive overhaul in the forthcoming transfer windows to tighten things up at the back.

A tale of 2 goalkeepers with contrasting fortunes

While Bernd Leno guarded the sticks for Arsenal with command, Kepa Arrizabalaga's performance came under immense scrutiny once again as the Spanish goalkeeper was beaten quite easily from Hector Bellerin's left-footed drive from the edge of the area. 

The former Athletic Bilbao man, who signed for a world record 72 million fee last summer, has been underwhelming to say the least this season and was once again at fault for the equalizer.

Arrizabalaga's 55.4% save percentage is the worst of any keeper in the Premier League this season and the Spaniard is ranked 127th out of 132 keepers in the top 7 European leagues - a stat that indicates that he has simply not been good enough since making the move to London.

Leno, on the other hand, has continued to grow in stature this season and the German international enhanced his reputation further with a string of crucial saves either side of half time. Arsenal, despite being reduced to 10 men, dug deep and secured a point and the Gunners have their goalkeeper to thank for keeping them in the game when the home side piled on the pressure.

Gabriel Martinelli is a superstar in the making

Gabriel Martinelli was an unknown commodity in the summer but when Arsenal announced his signature in the summer, there was a renowned sense of optimism amongst the Gunners faithful that the Brazilian hitman could be a superstar in the making. 

The youngster came with a reputation and hit the ground running immediately at the North London club and his tally of 9 goals and 2 assists in all competitions is a fantastic return for an 18-year-old playing his first season in Europe.

Martinelli was handed a rare league start last weekend in Pierre-Emerick Aubameyang's enforced absence and he made his opportunity count brilliantly, as he scored the Gunners' only goal of the game in their 1-1 draw against Sheffield United. 

Against a quality side like Chelsea, the Brazilian capped off a fine all-round performance with a sensational solo effort, as he ran the length of the pitch and slotted the ball past Arrizabalaga with relative ease to restore parity in the second half.

Aside from his finishing, Martinelli's work-rate coupled with his calmness in front of goal at such a young age has seen him develop into one of the most exciting players in world football and the Brazilian could be a vital player for the Gunners in the present as well as the future.