Arsenal would have confirmed Champions League football with a win on Thursday. But Arteta's side were beaten by Spurs 3-0 in the Premier League, which means the top-four race continues.
Arteta had criticized the performance of referee Paul Tierney following the loss, with Rob Holding having been sent off and Tottenham awarded a contentious first-half penalty.
Morgan has found fault with the Gunners manager throughout the season, lamenting the Spaniard for his handling of former captain Pierre-Emerick Aubameyang.
And his latest outburst comes following the Gunners' disappointing loss in the north London Derby, where he tweeted (via Independent):
“Arteta can moan as much as he wants but we bottled it tonight, and in a north London derby that’s unforgivable.”
He added (via Mirror):
"Can Arteta-crazed Arsenal fans remind me again why I should trust a process that involves spending £250million in two years, giving our best striker to Barcelona, and losing five of our last 10 league games in a crucial run-in with nothing else to play for? I'm struggling."
A huge final two games for Mikel Arteta's Arsenal
The 3-0 loss to Tottenham has allowed Antonio Conte's men back into contention for the top four, with just a point separating the two north London rivals with two games remaining.
Arsenal travel to St James' Park on Monday, May 16 to face a tricky Newcastle United side who have been in fine form.
The Magpies were loitering in the relegation spaces for the first-half of the season until Eddie Howe took over in November.
The former Bournemouth manager has overseen a remarkable turnaround on Tyneside that has lifted Newcastle up into mid-table.
Howe's side are playing with real confidence and hunger and have caused plenty of problems for sides, with the likes of Bruno Guimarães and Joelinton flourishing.
Following Monday's game, Arsenal's final game of the season is a home game against relegation-threatened Everton.
Given Frank Lampard's work in having the Toffees stave off the threat of relegation, they could be a nuisance.
Everton are currently 16th, two points ahead of 18th placed Leeds United with a game in hand.
But should Lampard's side go into the game at the Emirates on the final day of the season still in the relegation scrap, it could be a huge challenge for Mikel Arteta's side.