Chelsea tripped on Fulham and didn't even earn a point at home, which would likely cause them to drop to the 3rd place and be overtaken by Arsenal, if the Gunners win against the 19th Ipswich tonight at home, which is very likely.
But has anyone seriously expected that halfway through the season we would see Nottm Forest on the 3rd place? They are performing surprisingly well even though their performance is not at the top level i.e. they often get beating from the top clubs (e.g. even Man City in deep crisis beat them 3-0) but they are consistent in scoring 3 points when playing against weaker clubs. Yesterday's victory over Tottenham was their 4th consecutive win in the league.
Another bad game by Man United, they've lost to 17th Wolverhampton (2-0). The red card for Fernandes played a part here, but that's not much of an excuse. They are now getting closer to the relegation zone, being (8th points away from the 18th place) and they have difficult games ahead, against Newcastle and then Liverpool.