José Mourinho has written off Chelsea's chances of regaining the Premier League title and publicly questioned his players' attitude and "mentality" after his side slipped to defeat at Crystal Palace.

John Terry's own goal proved decisive as Palace beat these opponents for the first time in the league in 24 years, with Chelsea's second successive away defeat handing the initiative firmly to Manchester City and Liverpool in the title race. City, however, failed to move to the top of the Premier League after Saturday's 1-1 draw against Arsenal.

Mourinho had an altercation with a ball boy, which ended with a hug and handshake, before the end as frustration briefly flared, but made a beeline for the home dressing room post-match to congratulate Tony Pulis and his players on their victory.

"I think now we have lost any chance of finishing first," Mourinho said. "Now we depend too much on other results. Too much. When you depend a little it's possible, but when you depend a lot, I don't think it is.

"Six matches for us, and others with matches in hand … I know mathematically it's possible, but one thing is mathematics and another is reality. We are not [contenders]. I don't think it will happen: we depend too much on other results, and the other teams control what they need. I don't think we can win the league now.

"I know that Mr Foy's weekend [when the referee oversaw the loss at Aston Villa earlier this month] was an important weekend in this run, but today we threw away three points. We lost against a team who are difficult, but against a team who were better than us in terms of spirit and mentality. That's the last thing my teams are usually guilty of: normally, they don't lose because the opponents are stronger in terms of spirit."

Asked what had cost his side, Mourinho explained: "Mentality, and a little bit of quality. Mentality because the opponents beat us clearly on that: they were strong, aggressive, committed. Every one of them played at the top of their potential and that, in football, is important. And, after that, I think also we missed some qualities. The same qualities we've missed in every match we lost except Villa. At Stoke, Newcastle, Everton, Palace and drawing at West Brom … you try to find common points, and you do find them.

"Clearly we have some players because of their profile who find it difficult to perform in some kinds of matches. You have Branislav Ivanovic, John Terry, Gary Cahill and César Azpilicueta who perform in the sun, in the rain, on small pitches, on big pitches, against aggressive teams, against non-aggressive teams, against possession teams, against non-possession teams, and they perform every game from day one to the last day. And you have other players who are fantastic in some matches and disappear in others. You can find easily in these matches something in common. You can find it clearly."

Asked what quality is required for his side, Mourinho said: "I cannot say in front of the cameras. I can write it on paper." Offered a notepad afterwards, the Portuguese wrote "balls".

Mourinho had approached the ball boy in front of the main stand as time ticked down on the match, wary as he apparently was that Azpilicueta, the Chelsea player seeking to take a throw-in, might allow emotions to get the better of him. Eden Hazard was banned last season after clashing with a ball boy in the Capital One Cup semi-final at Swansea. "I was afraid Azpi was going to lose his emotional control and might push the kid or do something, so I went there," Mourinho said. "I told him not to do that [waste time] because he has the risk of one of my players punching him or losing his temper.

"The kids are educated to do this, but if a player hits a ball boy, the person who educates them disappears. The player stays in trouble for pushing or punching or kicking the kid. I had the chance to speak with the kid, who was cute. He came to me and I told him if he does this, one day somebody will punch him. I told him. Last year, what happened with Eden, you know … But the kids, it's not their fault. The kid just said, 'Yes'."