Peter Richards’ converted try at the end of a dreadful first half proved the difference as the game degenerated into a kicking duel.
Gloucester fly-half Ludovic Mercier finished with 14 points to Glen Jackson’s nine from three second-half penalties.
It was, so the euphemism goes, one for the purists. In sheeting rain, neither side were even remotely interested in playing with any width or invention.
Mercier and Mike Tindall were so limited in their outlook that the only time James Simpson-Daniel, Gloucester’s genuinely exciting centre, received decent attacking ball was from picking off misplaced Saracens passes.
The direct approach has been the cornerstone of Saracens’ game-plan this season, but it was Gloucester’s grunt and grind which gave them the best of the first half.
Saracens rarely managed to work their way into Gloucester territory during the opening 40 minutes and it required a rare spark from Thomas Castaignede to threaten a score.
The French full-back swept up a Mercier grubber kick under his own posts and slipped a clever inside ball to Glenn Jackson as Saracens countered.
The New Zealand fly-half kicked forward for Castaignede, who had continued his run down the left wing and into the Gloucester 22, but the visitors mopped up.
The defences of both sides were winning the day to such an extent that bookmakers were being contacted for odds on a 0-0 draw.
Eventually, after Mercier had missed a penalty and a drop goal, the breakthrough came just seconds before the interval.
Saracens were down to 14 men following the sin-binning of lock Kris Chesney for an offence at the lineout and Gloucester took advantage by opting for a lineout instead of a tough shot at goal.
The pack ploughed forwards at an angle towards the posts, where Richards touched down.
Mercier’s simple conversion earned Gloucester a 7-0 half-time lead – when both sides were booed off by the 6,493 hardy souls inside Vicarage Road – and Chesney was still off when Mercier extended it with a penalty immediately after the restart.
Gloucester were once again working field position more effectively but Saracens kept in touch as the game turned into a kicking duel between Mercier and Jackson.
Each fly-half landed three apiece – taking the score to 19-9 – before Gloucester botched a real chance of a break when Tindall spilled a pass from Mercier.
It was a disappointing day all round for the England centre with the RBS 6 Nations kick-off just a month away.
England prop Phil Vickery ended the game in the sin-bin for a late tackle on Jackson but Saracens could not force their way downfield to even earn a shot at the bonus point.