Alan Smith says Arsenal are playing like a side whose season has finished and feels they must now be "extremely careful" to avoid missing out on a Champions League place.
The Gunners' 0-0 draw with Sunderland at the weekend means they cannot now win the Premier League, with a place in the top four the final objective remaining for Arsene Wenger and his players.
They are currently five points clear of fifth-placed Manchester United but Smith is concerned his old team have lost momentum as a result of their failure to maintain a bid for the title.
Smith, who scored 115 goals in 347 games for Arsenal between 1987 and 1995, says they urgently need to motivate themselves if they are to avoid missing out on a 19th consecutive Champions League finish.
"They've got to be extremely careful because they're not in the best of form and you hope the players can lift themselves," he told Sky Sports News HQ.
"Sometimes it is difficult to rally the troops to finish fourth - you're not actually going for any silverware - but it's hugely important for Arsenal.
"Manchester United are breathing down their necks and it's a challenge. Arsene Wenger has always done it and you fancy them to do it again.
"But there's an element of 'the season's over' for them and the players have been unable to sustain that title challenge.
"The shoulders drop a little bit and they come off it five or 10 per cent, that can be costly. They need to go again now really."