Martinelli’s double and Bukayo Saka’s deflected effort made it 3-0 before half-time as the Gunners ruthlessly capitalised on an error-strewn Leeds performance
Raphinha pulled one back from the penalty spot in the second half, before Arsenal substitute Emile Smith Rowe wrapped up an emphatic victory for Mikel Arteta’s side late on.
“I think we did our job and we played so well. It was a great performance,” Martinelli told BBC Sport. “I was trying to score more but the most important thing is the victory.”
The scoreline could have been greater but for an impressive performance by Leeds goalkeeper Illan Meslier, who made fine stops to deny Saka, Alexandre Lacazette, Thomas Partey and Kieran Tierney.
Youngsters inspire Gunners to dominant win
On Christmas Day last year Arsenal were 15th in Premier League and only four points above relegation zone. Twelve months on and they are guaranteed to be in the top four on 25 December for the first time in five years.
Mikel Arteta is looking to build his side around a core group of young players and the fact all four goals were scored by players aged 21 or under suggests that policy is starting to bear fruit.
They were helped by some sloppy Leeds defending, but the Gunners front four of Saka, Martinelli, Martin Odegaard and Lacazette ruthlessly capitalised on any mistakes.
They managed 11 shots on target in the first half, the most by any side in the opening 45 minutes of a Premier League match since Opta started registering such statistics in 2003-04.
All this was achieved without striker Pierre-Emerick Aubameyang, who was left out of the squad following a disciplinary breach.
Martinelli is one of the players to benefit from Aubameyang’s absence, starting five successive Premier League games for the first time in his Gunners career.
“I’m so happy. Five games in a row [starting]. I’m trying to give my best on and off the pitch,” added the 20-year-old, who joined Arsenal from Brazilian club Ituano in July 2019.
“We know how difficult the Premier League is. We need to play well every game and try to win every game.”
Arsenal have reported an incident of alleged racism, with Gunners substitute Rob Holding approaching the fourth official in the 33rd minute and saying he had heard racial abuse from a Leeds supporter.
For Leeds, the defeat caps a difficult week that has included a last-gasp defeat at Chelsea and 7-0 hammering at Manchester City, though their cause has not been helped by a crippling injury list which has now robbed boss Marcelo Bielsa of 10 players.
It meant Robin Koch was forced back into action for the first time since the opening game of the season despite not being fully match fit, while the substitutes bench was made up of academy players, including 15-year-old Archie Gray.
Things then got worse when Jack Harrison was forced off after 30 minutes and replaced by 20-year-old Crysencio Summerville.
If little could be done to prevent their long casualty list, their problems on the pitch were largely of their own making.
Leeds players were guilty of repeatedly giving the ball away in dangerous areas, with only the impressive Meslier preventing Arsenal from scoring more.
They showed spirit to fight their way back into the game in the second half, and the Elland Road crowd continued to loudly back the players and manager Bielsa.
But the defeat makes it just one win in eight Premier League games, leaving the club just four points above the drop zone in 16th having played three games more than 18th-placed Burnley.