Cameroon international Bassong, signed from Tottenham last summer, battled against a recurring knee problem for much of the campaign, while Turner missed the final few weeks with a groin problem.
However, the rest of the Canaries' squad, including summer signings Holland forward Ricky van Wolfswinkel, England Under-21 winger Nathan Redmond, Sweden defender Martin Olsson and Dutch midfielder Leroy Fer, have all made the trip to the west coast.
The East Anglian club, who are training at Stanford University, will play Mexican side Dorados on Thursday evening before taking on Major League Soccer sides San Jose Earthquakes and Portland Timbers.
Manager Chris Hughton was set to link up with the 25-man squad on Wednesday after, according to the club website, finalising some pre-season plans back in England which could well include a move for Celtic's wantaway striker Gary Hooper - the subject of several bids in January.
Assistant manager Colin Calderwood believes the decision to leave Bassong and Turner to work on their fitness in England will help speed up their recovery, with final pre-season games set for Brighton, Braga, Real Sociedad and Panathinaikos ahead of the campaign opener against Everton at Carrow Road on August 17.
Speaking to the club's official website, www.canaries.co.uk, Calderwood said: "I think it was better for the ones left at home, Seb and Michael especially, to stay there. They wouldn't have taken part in any of the games over the 10-12 days.
"You can't go straight into the work at too high an intensity. The first thing that we have got to do is make sure that we have got as many players training for 100 per cent of the sessions that we have got - so that they don't miss a session."
- Sports & Recreation
- Ricky van Wolfswinkel
- Nathan Redmond
- San Jose Earthquakes