Warriors missed out on a bonus point and their 50th European Challenge Cup victory on a flithy Friday night in Newport which was marred by the sending-off of loosehead prop Ethan Waller.
Waller received a red card from French referee Ludovic Cayre, following the intervention of one of his assistants, for an alleged shoulder to the head. Waller look perplexed by the decision but his departure effectively ended any hopes Warriors had of a first win at Rodney Parade.
By that stage Warriors were already chasing the game having been punished by Dragons fly-half Sam Davies who kicked 20 of his side’s points – six penalties and a conversion of Adam Warren’s early try.
Warriors were slow out of the blocks and found themselves 13-0 down after 16 minutes before they rallied bravely and briefly went into the lead, 16-13, early in the second half thanks to the accurate kicking of Duncan Weir and a well-taken try from Tom Howe.
But Warriors again turned over too much possession and conceded too many penalties in the final quarter and now need to beat Enisei-STM and Castres at Sixways when the competition resumes next month if they are to progress to the quarter-finals for the second successive season.
Heavy rain, which started two hours before kick-off and continued throughout the match, ruined the contest as a spectacle and led to a high error-count from both sides.
Warriors also complicated matters by conceding a soft penalty from the kick-off for a late challenge on Dragons scrum-half Rhodri Williams which gave the Welsh side the position from which they were able to work centre Adam Warren over for a third minute try which Davies converted.
Further Dragons drew Warriors offside and Davies stretched the lead to 13-0 with two more penalties before Warriors had managed to venture more than a few yards into home territory.
But Warriors trimmed the deficit with Weir’s first penalty midway through the first half and were rewarded for further pressure when Weir banged over another penalty from long range on the half-hour. Dragons though left wing Ashton Hewitt had scored from a charge-down but play was brought back for an earlier infringement just inside the Dragons’ half.
Those scores lifted Warriors who thought they had been rewarded for a period of sustained pressure when Jono Lance, who took over the captaincy after Niall Annett departed with a shoulder injury, went over.
But the referee had already blown after one of his assistants drew his attention to an off-the-ball tangle which led to Cornell du Preez and Hewitt being sin-binned.
Warriors were awarded the resulting penalty which they opted to kick to the corner. Although Warriors knocked on as they drove from the lineout, Dragons also fumbled when they tried to attack from deep and when they collapsed the scrum, Weir applied the punishment to reduce the gap to four points on the stroke of half-time.
Warriors went ahead six minutes into the second half when Weir put in a pinpoint accurate Crossfield kick which Howe snaffled to touch down with Weir adding the conversion.
But Davies levelled again within four minutes and he banged over three more penalties in the final quarter to send Warriors home empty-handed.
Warriors | 15 Chris Pennell, 14 Perry Humphreys, 13 Ashley Beck, 12 Jono Lance, 11 Tom Howe, 10 Duncan Weir, 9 Francois Hougaard (Heaney 65), 1 Callum Black (Waller 55), 2 Niall Annett (C) (Miller 19), 3 Nick Schonert (Palframan 63), 4 Anton Bresler (Clegg 75), 5 Graham Kitchener, 6 Ted Hill, 7 Sam Lewis (Black 78), 8 Cornell du Preez (van Velze 63).
Replacements | 16 Isaac Miller, 17 Ethan Waller, 18 Richard Palframan, 19 Justin Clegg, 20 GJ van Velze, 21 Michael Heaney, 22 Noah Heward, 23 Nick David.
3m | Warren try 5-0
4m | Davies con 7-0
9m | Davies pen 10-0
16m | Davies pen 13-0
20m | Weir pen 13-3
31m | Weir pen 13-6
40m | Weir pen 13-9
46m | Howe try 13-14
47m | Weir con 13-16
50m | Davies pen 16-16
59m | Davies pen 19-16
68m | Davies pen 22-16
74m | Davies pen 25-16