Do you think Chelsea consider Burnley a "rival" and don't want to sell players to them? There is a line to be drawn somewhere over who is a rival for league positions and I think Swansea are below Southampton's line. Southampton's rivals for league position this season are Man Utd, Arsenal, Liverpool, Spurs and possibly West Ham.
Saints loaned Ramirez to Hull because they knew we would finish higher than Hull and Hull weren't a threat (cue posts saying Ramirez weakened Hull ).