Portsmouth suffered a sorry start to life in Sky Bet League Two as they crashed to a 4-1 home defeat at the hands of Oxford.
Pompey are considered one of the favourites for promotion and things looked promising for Guy Whittingham's relegated side when they took a 25th-minute lead through Patrick Agyemang in front of a league-record 18,000 strong crowd at Fratton Park.
However, Oxford had not read the script and they turned things round to go into the break 2-1 up with goals from Deane Smalley and Alfie Potter.
Things got worse for Portsmouth just before the hour-mark when they lost Johnny Ertl to a red card and Oxford made the most of their numerical advantage to add salt to their opponents' wounds with further goals from Potter and Smalley.
While it was an opening day to forget for Pompey, promoted Newport enjoyed a fairytale start on their return to the Football League with a 4-1 home win over Accrington.
A brace from Chris Zebroski and goals from Harry Worley and Christian Jolley handed Justin Edinburgh's side the points in Newport's first game back in the top four divisions since 1988, with Danny Webber scoring a consolation for Stanley.
Mansfield, who were promoted alongside Newport, could not match the Welsh side as they lost 2-0 to Scunthorpe, for whom Matt Sparrow and debutant Sam Winnall were on the mark.
Fleetwood, who like Portsmouth are also fancied to go up, started their campaign with a 3-1 home win over Dagenham and Redbridge with debutants Mark Roberts, Jeff Hughes and Ryan Cresswell all on the mark for the victors. Rhys Murphy replied for Dagenham.
Another club tipped to do well, Cheltenham, were forced to settle for a point after Burton hit back from two goals down to earn a 2-2 draw at Whaddon Road.
Hosts Cheltenham took control with goals from debutant Jamie Cureton - who was stretched off after being clattered as he guided the ball into the net - and his replacement Byron Harrison but Burton recovered through efforts from Billy Kee and recent arrival Rory Delap.