Cardiff Blues escaped with a 16-15 win over Ulster in the Magners League on Friday, but visitors Ulster were left rueing several missed opportunities from the tee which could have swung the game their way.
The result, if not the patchy performance, eases the pressure on Blues coach Dai Young, criticised for putting out a weakened side which lost at the Ospreys in midweek.
The home side's only try came from Leigh Halfpenny, with BJ Botha and Isaac Boss crossing for Ulster, but Blair's kicking proved decisive as he claimed 11 points.
With three games - against the last three Magners League winners - in six days, Young was in an invidious position and opted to concentrate on the two home games.
After a draw last weekend with Leinster, victory in this one was essential.
The Blues played some expansive rugby in the opening minutes, with wing Halfpenny going close after a kick-and-chase. But after a calamitous 30 seconds which involved three loose passes and a charged-down kick, they seemed to opt for safety first.
However, the back-row moves close to the breakdown which gained ground against Leinster were being swallowed by the Ulstermen, who used good ball off the tail of a lineout to put new South African prop Botha over wide out.
For the rest of the first half the boot dominated, Blair kicking two penalties each side of a reply by Ulster fly-half Niall O'Connor.
Ulster's rampaging pack, which featured captain Rory Best leading by example, kept things tight.
And when home fly-half Nicky Robinson was off target with a second drop-goal attempt just before the interval, he was greeted with a volley of boos by the disgruntled Blues fans.
They were cheered by a break from Jamie Robinson to open the second period, but the centre's pass out of a tackle went behind the unmarked Halfpenny and into touch.
Slow ball was hampering the home backs and a careless pass by scrum-half Darren Allinson was grabbed by Ulster replacement Thomas Anderson, who set off on an 80-yard gallop towards the Blues line, only to be hauled down by the quicker Halfpenny.
Blair hit a post with a penalty as the Blues kept up the pressure and they were finally rewarded when Halfpenny took an inside pass from substitute fly-half Ceri Sweeney to go over under the posts. Blair converted.
Ireland wing Andrew Trimble showed fine hands to threaten on both sides of the field as Ulster fought back, but after a spell of sustained pressure scrum-half Boss shrugged off some feeble tackling for a try improved by Connor.
But Blair quickly slotted a penalty to regain the lead for the Blues and the home side held on in a nail-biting finale.
For Cardiff Blues:
Pens: Blair 3
Tries: Botha, Boss
Cardiff Blues: 15 Ben Blair, 14 Leigh Halfpenny, 13 Jamie Robinson, 12 Gareth Thomas, 11 Chris Czekaj, 10 Nicky Robinson, 9 Darren Allinson, 8 Mark Lewis, 7 Martyn Williams, 6 Maama Molitika, 5 Paul Tito (c), 4 Bradley Davies, 3 Gary Powell, 2 T Rhys Thomas, 1 Gethin Jenkins.
Replacements: 16 John Yapp, 17 Gareth Williams, 18 Scott Morgan, 19 Andy Powell, 20 Jason Spice, 21 Ceri Sweeney, 22 Jamie Roberts.
Ulster: 15 Clinton Schifcofske, 14 Andrew Trimble, 13 Darren Cave, 12 Rob Dewey, 11 Timoci Nagusa, 10 Paddy Wallace, 9 Isaac Boss, 8 Robbie Diack, 7 David Pollock, 6 Matt McCullough, 5 Ed O'Donoghue, 4 Ryan Caldwell, 3 BJ Botha, 2 Rory Best (c) 1 Justin Fitzpatrick.
Replacements: 16 Nigel Brady, 17 Tom Court, 18 Kieron Dawson, 19 Tom Anderson, 20 Cillian Willis, 21 Niall O'Connor, 22 Bryn Cunningham.
Referee: Alan Lewis (Ireland)
Assistant Referees: Hugh Watkins (Wales), Steve Edwards (Wales)
Television Match Official: Gareth Simmonds (Wales)