Saracens gave new coach Brendan Venter the perfect start his reign by edging out London Irish 18-14 at Twickenham on Saturday.
The Vicarage Road outfit took an 18-3 lead into the break thanks to a try, conversion and two penalties by Glen Jackson, and another touchdown by Andy Saull.
A below-par Irish side fought back in the second half but, despite George Stowers' try and penalties by Ryan Lamb and Delon Armitage, they could not complete the comeback.
The two clubs have experienced contrasting summers. Irish made a couple of astute signings but kept the vast majority of the squad that took them to the Premiership final last season.
Saracens, meanwhile, gave themselves a spring clean, with 12 players coming into a club that now has a largely South African accent. Indeed their new coach is 1995 World Cup-winning Springbok Venter.
And it was Sarries who first troubled the scorers, the reliable Jackson knocking over a third-minute penalty.
The Exiles, tipped to shrug off their 'nearly men' tag this term, replied in kind in the ninth minute through Lamb, who made up for an earlier missed penalty to stroke another more straightforward one through the sticks.
Brought in from Gloucester for the departed Shane Geraghty, Lamb's touch-finding was impressive but both back lines were feeding off scraps.
Jackson's try, therefore, came somewhat out of the blue. Irish lock Nick Kennedy failed to rollaway at a maul, and after a bout of handbags between both sets of forwards, the England international got a ticking off.
In the meantime, his side had failed to organise themselves for the resulting penalty. Most were thinking Jackson was going to kick at goal but he chose to run the penalty and dummied his way over the line from 20 yards.
The Kiwi converted his own try and knocked over a penalty soon after to put Sarries 13-3 up after 26 minutes.
Irish were making silly errors and they slipped further behind eight minutes later.
Alex Goode and Chris Wyles cut the Exiles' defence to ribbons down the left and, when the ball was set up, Jackson sent over a cross-field kick behind a stranded defence for Saull to ground.
Jackson missed the extras but Saracens were 18-3 ahead at the break.
Lamb wasted a chance to reduce his side's arrears when he was off target with a 44th-minute penalty and then with a simple kick eight minutes later.
Both sides were reduced to 14 men when Armitage and Schalk Brits were yellow-carded for their parts in a mini-brawl, before Lamb did find his range from 20 yards for 18-6.
Saracens went down to 13 players with 20 minutes left after Ernst Joubert was cautioned and Stowers made them pay when he burrowed over from close range after Irish had turned a scrum to earn the put-in.
Lamb missed the conversion, though, to leave his men still seven points behind.
But Saracens were by now hanging on and the Irish were finding holes in the opposition defence.
Armitage, replacing the substituted Lamb as kicker, booted over a penalty with seven minutes remaining to make it a four-point game.
Saracens held on, though, to start the season with a victory.
Tries: Jackson, Saull
For London Irish:
Pen: Lamb 2, D Armitage
Saracens: 15 Alex Goode, 14 Noah Cato, 13 Kameli Ratuvou, 12 Brad Barritt, 11 Chris Wyles, 10 Glen Jackson, 9 Neil de Kock, 8 Ernst Joubert, 7 Andy Saull, 6 Wikus van Heerden, 5 Hugh Vyvyan, 4 Steve Borthwick (capt), 3 Carlos Nieto, 2 Schalk Brits, 1 Rhys Gill.
Replacements: 16 Fabio Ongaro, 17 Tom Mercey, 18 Richard Skuse, 19 Mouritz Botha, 20 Michael Owen, 21 Justin Marshall, 22 Derick Hougaard, 23 Richard Haughton.
London Irish: 15 Delon Armitage, 14 Adam Thompstone, 13 Elvis Seveali'i, 12 Seilala Mapusua, 11 Sailosi Tagicakibau, 10 Ryan Lamb, 9 Paul Hodgson, 8 Chris Hala'Ufia, 7 Steffon Armitage, 6 Declan Danaher, 5 Andy Perry, 4 Nick Kennedy, 3 Paulica Ion, 2 Danie Coetzee, 1 Clarke Dermody (capt).
Replacements: 16 Dan Murphy, 17 James Buckland, 18 Faan Rautenbach, 19 Bob Casey, 20 George Stowers, 21 Peter Hewat, 22 Peter Richards, 23 Alfredo Lalanne.
Referee: Dave Pearson