Saints suffer Lawes and Biggar blows as they bow out of Challenge Cup at Gloucester
Biggar looks likely to face a ban for his high tackle, and that is set to rule him out of key Gallagher Premiership matches as Saints pursue a top-four spot.
Saints have bowed out of the Challenge Cup at their first hurdle, having dropped into the competition from the Champions Cup, and their five-match winning streak is over.
Gloucester simply proved too strong at Kingsholm, the ground where both of Saints' two most recent defeats have now come.
The Cherry and Whites flew into a 21-0 first-half lead, but Saints cut the gap to seven points at the break thanks to scores from Juarno Augustus and Rory Hutchinson.
That sparked hope of a comeback in the away camp, but Gloucester turned the screw in the second half, scoring through yet another inexorable maul before Biggar was dismissed.
Saints kept fighting with 14 men, and Mike Haywood grabbed their third score of the game.
But the deficit was too great and Gloucester were able to celebrate a win that propels them into the quarter-finals.
Saints had travelled to Kingsholm hoping to exact revenge for a gut-wrenching Premiership defeat at Kingsholm on March 5.
And Boyd's men had chance to take an early lead, but Biggar's penalty from a tricky position rebounded back off the right post to safety.
Gloucester soon made the most of their reprieve, scoring from their first real piece of possession of the game.
Ollie Thorley grabbed the ball close to halfway and scythed through Saints to etch his name on the scoresheet.
It was a fine finish and one added to by Adam Hastings, who didn't have to wait too much longer for his second conversion of the night.
George Furbank got trapped inside his own 22 and Gloucester showed real ferocity to get the ball back before a fine offload allowed Val Rapava Ruskin to score on the left.
Gloucester, and their fans, were fired up, and Saints were really up against it, having conceded two tries from just two attacks.
A bad start was to get worse soon after as Lawes was forced off with what appeared to be a hand injury.
Alex Coles came on for Lawes but the young forward was soon heading off the field for a spell in the sin bin as Gloucester turned the screw with their trademark mauling game.
It was far too much for Saints to handle as they conceded penalty after penalty, and finally the pressure told as Matias Alemanno got the ball down.
Hastings converted and at 21-0 down it was already a very long way back for Saints, who were struggling to come up with any sort of solutions to the power of the home side.
But the black, green and gold did manage to deal with being down to 14 men, and when Coles came back on, the away side had a platform from a penalty.
Gloucester splintered from their defensive lineout, allowing Augustus to go over for a try.
Biggar added the extras and Saints were hoping the seven-pointer could prove a catalyst before the break.
Hutchinson launched a quick break from close to his own try line, but Gloucester scrambled to stop Lewis Ludlam after the Saints skipper had gone past halfway.
But Hutchinson soon had his moment as a loose pass inside the Gloucester half fell into his path, and the Saints centre juggled the ball before cruising in for a simple score.
Biggar converted and Saints were just seven points behind at the break.
But the black, green and gold still had no answer against the Gloucester lineout drive after half-time, and another incredible surge towards the line ended in Santiago Socino scoring.
Hastings converted and the home side had their breathing space back.
Saints were hit by another blow on 52 minutes as Biggar was sent off for making shoulder contact with the head of Chris Harris.
Hastings notched the resulting penalty and Gloucester were in complete control inside the final half an hour of the match.
Saints kept battling away and they did manage to bag another try from a lineout drive, with Haywood the player to profit.
Furbank added the extras and Saints were 10 points down with 15 minutes to go.
The away side kept coming, earning a series of penalties in the Gloucester half, but they couldn't convert their opportunities.
Gloucester replacement Alex Craig was red carded just before full-time for striking the face of Coles, but the final whistle soon blew to confirm the hosts' win.
Gloucester: Carreras; Rees-Zammit (Seabrook 65), Harris, Atkinson, Thorley; Hastings, Chapman (Meehan 61); Rapava-Ruskin (Elrington 62), Socino (Singleton 61), Balmain (Ford-Robinson 38); Clarke (Craig 61), Alemanno; Reid, Ludlow (c), Ackermann (Morgan 65).
Saints: Furbank; Freeman, Proctor (Francis 63), Hutchinson, Collins; Biggar, Mitchell (James 63); Waller (Hobbs-Awoyemi 54), Matavesi (Haywood 54), Hill (Carey 63); Ribbans (Harrison 54), Ratuniyarawa (Nansen 61); Lawes (Coles 15), Ludlam (c), Augustus.
Referee: Sam Grove-White