It brings to an end a nine-game unbeaten run in all competitions, stretching back to mid-September, but of more concern to Jose Mourinho will be his team's continued struggles on the road.
The Blues have won just once away from Stamford Bridge all season, defeating Norwich City 3-1. It's a statistic that makes for uncomfortable reading, especially considering that solitary victory over the Canaries wasn't secured until the last five minutes courtesy of breakaway goals from Eden Hazard and Willian.
While at this early stage in the campaign that deficit can be recovered, if Chelsea's away form continues, they run the very real risk of being cut adrift in the title race.
"We deserved to lose," Mourinho said in his post-match press conference, reported by ChelseaFC.com. "Maybe they [Newcastle] didn't deserve to win, but for sure we deserved to lose."
And that's Chelsea's problem when they travel. They have rarely been outplayed thus far, but they have struggled to break teams down and have eventually succumbed to soft goals.
Newcastle's opener was a fine case in point. Normally strong from set pieces, the Blues defence was found wanting as Yohan Cabaye's free-kick was expertly dispatched by Yoan Gouffran on 68 minutes.
Having controlled the game until that point, when Newcastle upped the tempo, Chelsea didn't have an answer. Things became even more stretched after that, and Loic Remy finished them off in the 89th minute to make it 2-0.
"The first half was very easy to play," Mourinho continued. "We had lots of space, no real pressure from the opponent, but we were just waiting for the opponent to lose the ball. When they did we were not aggressive enough with it and we lost the ball after recovering it.
"We were too soft with and without the ball, but especially with it because we had it for a long time. We gave them 45 minutes of a friendly and it was only when they scored the goal we had a reaction. I think it was a really bad performance by us."
It was a performance in stark contrast to last week's 2-1 victory over Manchester City at Stamford Bridge, with Chelsea chasing victory until the final minute when Fernando Torres capitalized on a mistake from Matija Nastasic and Joe Hart to gun down their title rivals.
That day, the Blues were full of energy and stuck to their game plan, frustrating City. At St. James' Park, it was the home team again who had the advantage, with Chelsea on the receiving end.
|Chelsea's Away Form vs. Their Title Rivals|
All is not lost, of course, and Chelsea can take solace from the lessons they have learned in the past. It was at a similar stage in 2004-05—Mourinho's first season at Stamford Bridge—when they suffered a surprise 1-0 defeat away to Manchester City.
Arsenal, the defending Premier League champions, went five points clear that weekend with a 3-1 victory over Aston Villa. With eight wins in their next 10 league matches, the Blues chased the Gunners down and eventually took control of the title race.
Their away form was somewhat better back then, yet the experience could prove vital almost a decade on.
"I am worried," Mourinho told the gathered press in the St. James' Park media lounge. If things continue as they are, he should be.
Garry Hayes is Bleacher Report's lead Chelsea correspondent and will be following the club from a London base throughout the 2013-14 season. Follow him on Twitter here @garryhayes.