Tommy Bowe loses the ball in tricky weather conditions at the Liberty Stadium.
Jonathan Humphreys insists the Ospreys are hitting form at just the right time after regaining top spot in the Magners League.
Scotland wing Nikki Walker bagged a brace of first-half tries before skipper Ryan Jones sealed an emphatic Welsh derby victory over Cardiff Blues at the Liberty Stadium.
The result puts the Ospreys two points clear of Glasgow Warriors at the summit of the table and in good spirits ahead of a crunch month which includes mammoth Heineken Cup ties against Clermont Auvergne and Leicester Tigers.
Humphreys said: "It's good to be top of the league and that's where we want to be. We appreciate everyone else has games coming up but with the changes we made to our game, we always felt December and January would be defining months for us.
"The structure was good as was our defence. There are still things to work on but we believe things are coming right for us and our form is getting towards where we want it to be.
"We have to be in good shape going into the Heineken Cup and continue our momentum before facing Clermont."
Man-of-the-match Dan Biggar opened the scoring with a deft 12th minute drop goal on the way to an 11-point personal haul before Walker crossed at the end of the opening quarter.
Then Walker doubled his try count from close-range in the left corner following a neat break by fly-half Biggar and Jones added a third with a try just after the hour mark to leave the Blues white-washed.
Humphreys added: "We're pleased with the performance but it is disappointing that we didn't get the bonus point considering how early we scored the third try.
"We're delighted to keep them to nil and it's nice to achieve that against anybody. But it wasn't easy. There are a lot of battered and bruised bodies in the dressing room."
Blues coach Dai Young offered no excuses as his side are still searching for their away success in the league this season.
Young said: "Sometimes you have to hold your hands and say we were beaten by a far better side. It was a disappointing performance and the Ospreys controlled the field."
All roads lead to Cardiff on Sunday for the SSE SWALEC Finals Day at the Millennium Stadium. Cambrian Welfare tackle Ystradgynlais in the Bowl final, Ystrad Rhondda play Newcastle Emlyn in the Plate final while defending champions Pontypridd face Bridgend in the Cup final.
WRU Chief Executive Roger Lewis, Deputy Minister for Culture, Sport and Tourism Ken Skates and WRU Chairman Gareth Davies earlier this week launched a new competition in conjunction with the WRU unveiling its archive room.
Welsh players and management joined Deputy Minister for Sport Ken Skates at the Pierhead Building, Cardiff Bay earlier this week to reveal the Union's pioneering school-club hub initiative has been so successful the project will now almost double the scale of the original project.
The Scarlets, Newport Gwent Dragons, Cardiff Blues and the Ospreys look ahead to Judgement Day III which sees the Blues take on the Ospreys (2.30) and the Dragons tackle the Scarlets (4.45pm) at the Millennium Stadium tomorrow afternoon.
Ystradgynlais and Ynysddu played out a titanic struggle at Taffs Well in the SSE SWALEC Bowl semi-final. At the end of the game neither team could be separated after a 15-15 stalemate but Ystradgynlais go through on try count.
Blues strike first in JD III battle - Newport Gwent Dragons lock Andrew Coombs, WRU referee Dylan Llyr Jones and Cardiff Blues hooker Matthew Rees decide dressing room allocations for Judgement Day III
Wales Under 18 captain Calum Haggett has received a conditional offer to read Biomedical Science at St Anne's College, Oxford. WRU chairman Gareth Davies went to meet Calum and Coleg y Cymoedd Principal Judith Evans to wish him luck in his exams and pass on some of his personal experience.