The pundit said that Arsenal have gone from the "Invincibles" - the team that went unbeaten during the 2003/04 Premier League season.
Wenger's side have lost four successive away league games for the first time in his 21-year reign as manager.
Goals from Andros Townsend, Yohan Cabaye and Luka Milivojevic sealed the Eagles' impressive victory at Selhurst Park and heaped further pressure on Arsenal and under-fire manager Arsene Wenger.
"You could tell they wanted it more".
The result leaves Arsenal in sixth place and seven points off the top four with eight games left.
Hartson said: 'I worked under Arsene Wenger and I've always sort of been in the camp of "Arsene Wenger's great, he's done fantastic, the Champions League qualifications, the money that he brings into the club...", but I just think now it's time for him to go. "We have got incredibly hard games to come, so we are not getting carried away, but if we can beat Leicester things are looking good".
"After such a long time, to see that we've lost a game the way we've lost it is, of course, very disappointing".
With links to Premier League champions-elect Chelsea emerging after his contract talks were shelved until the summer, Sanchez's future at the Emirates looks as precarious as ever.
John Cross of The Mirror believes that there is a 95 percent chance that Arsene Wenger will sign a new two-year deal to stay at Arsenal.
The uncertainty over his future has been a major distraction for a team lacking the fighting spirit required to cope with adversity.
He had led Arsenal to top-four finishes in each of his previous 20 seasons at the helm.
"You understand that our fans are very unhappy". I'm not in the mood. I think we had a lot of the ball. "From the start onwards, in the decisive moments of the game, they were sharper".
At the other end, Wayne Hennessey had one of his easier nights in the Palace goal as Arsenal failed to muster a single shot on target in the second half.
"He's saying "from kick-off we knew straight away they were more up for it". On that front that is the most hard for us.
The 28-year-old maintained that whenever they go on the field, they try their best to win.
"The fact that we've lost a few away games: it's really unusual".
"You could sense it had an impact on us after the second goal".
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Police say they have arrested a second person in connection with the attack, but have given no further information. "I can confirm that a second person has been arrested ", Stockholm district court judge Helga Hullman said.