Pre-season favourites Southampton were brought down to earth by Plymouth Argyle as Luke Summerfield's strike ensured Peter Reid's side returned to Devon with all three points.
Elsewhere, Akpo Sodje 22nd-minute goal proved to be enough for Charlton Athletic to beat Bournemouth 1-0 while Dean Bowditch and Luke Freeman were on target for Yeovil Town in their 2-1 victory against Leyton Orient.
Richard Logan scored a late equaliser for Exeter City in their 2-2 draw against Colchester United, while Dagenham and Redbridge slumped to a 2-0 defeat at Sheffield Wednesday.
Scott Doe had the misfortune of putting the ball in his own net while Clinton Morrison grabbed the Owls' second goal.
Matt Sparrow scored twice as Brighton won 2-1 at last season's beaten play-off finalists Swindon Town while Gary Madine's goal midway through the first half put Carlisle United on their way to a 2-0 win against Brentford. Ian Harte scored the second goal from the penalty spot on the stroke of half time.
Dale Stephens scored twice as Oldham Athletic opened with a fine 2-1 win at Tranmere Rovers while Anthony Pilkington netted twice and Jordan Rhodes was also on the scoresheet as Huddersfield Town won 3-0 at Notts County.
MK Dons led at Walsall thanks to Sam Baldock's goal just before the interval. The Saddlers equalised immediately after the break through Emmanuele Smith but Dan Woodards grabbed the Dons' winner on the hour.
George Boyd and Aaron McLean both scored at London Road as Peterborough United beat Bristol Rovers 3-0 while Rochdale and Hartlepool United were involved in a goalless draw at Spotland.