Wigan Warriors began their Super League title defence with a 26-16 win at Salford Red Devils, while last year's runners-up Warrington Wolves suffered an opening-round defeat in Perpignan.
A dominant first-half display set up Wigan's triumph on Saturday, with the returning Joe Burgess, George Williams and Joel Tomkins - appearing in his first match since July due to a knee injury - adding to Oliver Gildart's double.
Rather than collapse after going into half-time 26-0 down, Salford rallied and closed the gap with scores from Kriss Brining, Junior Sa'u – who went off late with a head injury – and Michael Dobson.
Next up for the Warriors is 2016 NRL Grand Final winners Cronulla Sharks in the World Club Challenge on February 19.
Warrington take on Brisbane Broncos ahead of that fixture, but will do so on the back of a loss after going down 20-12 to Catalans Dragons.
The Dragons were without Tony Gigot, who has been banned by the French Federation after an alleged clash with a doping control officer despite not testing positive for a banned substance.
Andre Savelio marked his Wolves debut with a ninth-minute try, but Catalans hit back through former Warrington half-back Richie Myler.
Catalans lost Fouad Yaha to what appeared to be a serious ankle injury, but a try from Greg Bird - back at the club after seven seasons at Gold Coast Titans - and Luke Walsh's penalty put them in charge, with Brayden Wiliame securing the win after Rhys Evans had set up a tense finale.