England hopeful James Forrester underlined his autumn Test credentials with another try-scoring display as unbeaten Gloucester moved top of the Guinness Premiership.

The Gloucester number eight lit up an often dour Kingsholm struggle through a superbly-taken solo score midway through the first half.

It was Forrester's third try in successive league games following touchdowns against Harlequins and Leicester, suggesting England boss Andy Robinson will find it difficult to ignore him on current form.

England's opening Test of the season against New Zealand at Twickenham is just six weeks away, and 25-year-old Forrester continues to make powerful statements.

He was the one Gloucester player Northampton found difficult to handle, but Saints had enough problems of their own to cope with as captain Bruce Reihana and props Tom Smith and Pat Barnard all limped off injured.

Barnard's departure eight minutes from time led to uncontested scrums. His exit came immediately after the Gloucester forwards executed a stunning 30-metre drive that ended with flanker Andy Hazell touching down.

Fly-half Ludovic Mercier kicked 13 points for the home side as they made it three wins and a draw from four starts to edge above Wasps, who play Bristol tomorrow, with substitute Jack Adams claiming Gloucester's third try in injury-time.

Northampton, not helped by a mixed display from fly-half talisman Carlos Spencer, played much of the match on the back foot.

Centre David Quinlan's well-worked early try promised rich pickings for the travelling Saints fans, but once Gloucester's forwards turned the screw, there was only one winner.

Goalkicking ace Mercier returned to the Gloucester side as replacement for knee injury victim Willie Walker, who joined the likes of Mike Tindall, Iain Balshaw, James Simpson-Daniel and Alex Brown on a lengthening injury list.

Elsewhere, scrum-half Rory Lawson made his first Premiership start instead of a rested Peter Richards, while Gloucester head coach Dean Ryan also handed starts to prop Nick Wood and lock Adam Eustace.

Northampton though, were unchanged following a 33-18 victory over Bath last time out, with scrum-half Mark Robinson appearing just five days after being warned about his future conduct by the Rugby Football Union following an X-rated verbal blast at Bath wing Andy Higgins.

The early exchanges were tetchy as both packs grappled for control, and referee Sean Davey had his hands full before dishing out lectures to rival skippers Reihana and Marco Bortolami.

Reihana's afternoon ended prematurely, as he suffered a serious-looking injury to his right knee after chasing a steepling Spencer kick.

He hobbled off to be replaced by Luke Myring, giving Saints a potential headache in the outside centre position, given that Jon Clarke will be sidelined until at least Christmas because of a broken ankle.

Mercier put Gloucester ahead through a short-range penalty, but Northampton hit back within three minutes when Spencer made his first - and only - significant contribution.

The former All Blacks star recovered from an error-strewn opening by delivering a delicate kick into Gloucester's 22, and Quinlan gathered a kind bounce to touch down unopposed.

Kydd slotted the simple conversion before Spencer and Mercier missed long-range penalty chances as Gloucester looked to raise their performance level, especially in the lineouts where Saints enjoyed initial domination.

It took a flash of inspiration to lift Gloucester when Forrester exploited a huge defensive gap and raced 30 metres for his third try of the season.

Mercier converted, but tempers continued simmering away and Saints flanker Paul Tupai was sin-binned following a stamp on Forrester.

Gloucester though, could not maximise their temporary one-man advantage and Saints trooped off at half-time just 10-7 adrift.

Ryan replaced hooker Olivier Azam with Welsh international Mefin Davies for the second period, which started with Spencer fumbling possession inside his own 22 as Gloucester tried to increase the tempo.

Mercier slotted his second successful penalty before Smith followed Reihana on to the injury list and Saints' caretaker captain Steve Thompson grew increasingly exasperated with some of referee Davey's rulings.

Richards appeared off Gloucester's bench for the final 30 minutes, but the home side remained edgy and indecisive in attack before another Mercier penalty gave them a degree of breathing space at 16-7 ahead.

Then came Hazell's try as the Northampton pack capitulated under pressure, and Gloucester were home and dry with four more points safely collected as Saints ended a man short following a yellow card to Myring.