Having suffered their first Premiership defeat of the season in their last away game, the Exeter Chiefs lost again at Northampton Saints.
Premiership leaders Exeter Chiefs lost for the second league away game running as Northampton Saints edged a 31-28 victory on Friday.
Exeter were beaten at Harlequins late in November and they again come unstuck on their travels in a thrilling encounter at a raucous Franklin's Gardens as the Saints climbed to fourth.
Northampton made a flying start as Piers Francis tore through the Chiefs inside two minutes and Dan Biggar quickly added a second home try.
But that lead was wiped out as a series of infringements led to an Exeter penalty try, before Santiago Cordero crossed in the corner to tie an entertaining match.
Fraser Dingwall was influential in the hosts wresting back the momentum ahead of the break, going between the posts for a third try and holding up Ollie Devoto on the line after Alex Waller was sent to the sin bin from a scrum.
The Chiefs continued to push and the TMO confirmed Ben Moon's 44th-minute try to draw the sides level again.
A breakaway effort sent Northampton clear before the hour mark, Cobus Reinach seizing on a pass and sprinting through for the bonus point.
Luke Cowan-Dickie had only been on the field five minutes when he saw yellow for a dangerous double tackle on Courtney Lawes, giving Biggar the opportunity to kick a crucial penalty that kept the Saints in front even when Matt Kvesic crossed beyond the 80th minute.
Calum Clark and David Strettle scored second-half tries as Saracens rallied to beat Worcester Warriors, while Harlequins held off Wasps.
Saracens closed the gap on Premiership leaders Exeter Chiefs by producing a second-half fightback to beat Worcester Warriors on Saturday.
With the table-topping Chiefs surprisingly slipping up at Northampton on Friday, another upset appeared on the cards when Worcester held a 17-11 half-time lead at Allianz Park.
However, the reigning champions rallied impressively after the break, tries from Calum Clark and David Strettle helping the hosts record a 25-17 triumph that leaves them just a point behind Exeter after 11 matches.
In the day's late kick-off, Harlequins made a fast start and held firm in the closing stages to record a 20-13 victory over Wasps in front of a sell-out crowd at Twickenham.
Alex Dombrandt touched down inside a minute and a pair of Marcus Smith penalties helped put Quins 13-3 up at the break, though their opponents hit back early in the second half when Will Stuart touched down.
Crucially, though, Quins scored the next try, Joe Marchant stretching out to ground Danny Care's clever grubber kick in behind the defensive line. Smith landed the conversion and while Lima Sopoaga's penalty put Wasps within striking distance, they were unable to make their late pressure tell.
At Kingsholm, Sale Sharks continued their surge up the table by upsetting Gloucester, who let slip an early 10-point advantage to lose 30-15 at home.
Chris Ashton, Faf De Klerk, Rob Webber and Denny Solomona all touched down for the in-form Sharks, who claimed a bonus-point win on their travels to move up to sixth place.
Bristol Bears ended 2018 with a huge win over Newcastle Falcons, while Bath moved up to fifth with victory over Leicester Tigers.
Newcastle Falcons remain bottom of the Premiership table after Tom Pincus' late try gave Bristol Bears a 35-28 win, while Bath saw off Leicester Tigers 23-16 in Sunday's other top-flight fixture.
The struggling Falcons led 20-10 at the break at Ashton Gate but Bristol came roaring back in the second half to claim only their fourth top-flight win of the season, moving them six points clear of their opponents.
Harry Randall got Pat Lam's men off to a dream start, taking an offload from Luke Morahan to score the opening try in the first minute, but it was advantage Newcastle at the interval following five-pointers from Vereniki Goneva and Callum Chick.
While two tries in the space of five minutes from Charles Piutau and Morahan - plus a second penalty from Ian Madigan - gave Bristol a five-point lead, Adam Radwan got on the end of a Toby Flood grubber kick to make it 25-25.
Callum Sheedy and Flood traded penalties as the tension mounted and it was Bristol who snatched it in the closing stages, Pincus stepping inside to finish after an incisive run from Ed Holmes, claiming not only a huge win but also a welcome bonus point.
Meanwhile, Bath moved up to fifth in the standings thanks to a home win over Leicester.
The Tigers are just one point ahead of Bristol after Jamie Roberts, Nathan Catt and Ruaridh McConnochie went over to give Bath back-to-back league victories, Jonny May's try and 11 points from the boot of George Ford against his former club proving to be in vain for the visitors.