Saints, quarter-finalists last season, scored four tries at Franklin's Gardens in a nervy Pool Four encounter.

The English champions led 14-0 at half-time thanks to efforts in tricky conditions by James Pater and Toby Thame.

Tenacious Cardiff struck back through Harri Millard and Mason Grady to make it a two-point game in the final quarter.

But George Hendy and Fraser Dingwall responded as Northampton got off to a winning start, albeit without a bonus point.

Northampton's success came at the end of a chastening opening weekend of the top-tier tournament for Prem clubs, with Gloucester drawing against champions Bordeaux-Begles but six other sides losing.

Cardiff's return to the top tier of Europe after two seasons in the Challenge Cup was a considerable one.

Saints had scored 24 tries in their three opening fixtures of their Prem title defence, including 11 against Bath last time out at Franklin's Gardens.

The Welsh side also had to contend with a five-day turnaround to a United Rugby Championship (URC) fixture against Sharks at Cardiff Arms Park.

That led to several influential players being held back, although they did give first appearances of the season to Wales and Lions internationals Taulupe Faletau and Josh Adams after injury.

Northampton also made changes because of a big fixture on the horizon - the short trip to Leicester on Saturday - but got the job done.

Full-back Pater opened the scoring for Saints with a supporting run and centre Thame crashed over after 20 minutes.

Both Northampton number eight Callum Chick and Cardiff lock Tom Manz knocked on going for the line as slippery conditions led to it being 14-0 at half-time.

The Blue and Blacks struck back early in the second half when centre Millard hit a nice line in the 22 and then defended stoutly to frustrate their hosts, forcing them into a raft of handling errors.

It was 14-12 on the hour when, after Saints fly-half Anthony Belleau was sin-binned for a breakdown offence, the ball was floated to the right by Jarrod Evans for Grady to cross.

Cardiff scented an upset only for Hendy to respond swiftly, juggling the ball for a try that Pater converted.

The Northampton wing went from scoring five points to saving them by chasing down Adams when a try seemed certain.

Dingwall dashed over in the 78th minute but the hosts could not find the fifth try that was needed for a five-point haul.

Saints travel to Stade Francais in December and return to France in January to face Montpellier before a home finish to the group stage against Bulls.

Cardiff host Bath in December and then face a pair of French teams in January, travelling to Stade Francais and entertaining Montpellier.

Line-ups

Replacements: Langdon, Els, Neculai, Prowse, Ulcoq, McParland, Smith, Dingwall.

Yellow card: Belleau 60.

Replacements: E Lloyd, Barratt, Cowell, McNally, De La Rua, S Davies, Sheedy, Adams.