They also suffered 23-11 and 14-11 defeats to Scottish rivals Edinburgh in consecutive weeks to lose the 1872 Cup for just the second time in seven attempts.
However, the Warriors will now turn their attention to European matters as they travel to Stade Yves-Du-Manoir to take on Racing 92 this weekend before facing Northampton Saints and a return fixture with Racing to round out the Champions Cup group stages.
And fly-half Weir is confident that a few weeks away from the GUINNESS PRO12 will do his side a world of good.
"We switch competitions now for three weeks and there's no better opportunity than to go away to Racing this weekend, come away with a victory and keep building on that," Weir said.
"We're bitterly disappointed with the results over the past two weeks against Edinburgh. We need to go to Racing and put on a great performance, which is in the locker from us.
"We just killed ourselves as a team in that second half against Edinburgh in the second leg. It's the small margins in rugby to make a team click.
"Against Edinburgh in the second leg I thought the forwards in that first half were absolutely outstanding and we left a couple of tries out there. If you go in with a couple more tries you can push forward.
"We didn't play in the right areas in the second half and that put a wee bit pressure on us and we gave away some really soft penalties and that meant we didn't really get any momentum in that second half."
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