Leicester target Nicky Maynard scored twice for Bristol City to condemn the promotion favourites to a 2-1 home defeat.
The Foxes are expected to launch a serious npower Championship promotion push but after a 2-0 defeat at home to Reading at the weekend, could only follow it with a second successive loss tonight.
Maynard put Bristol City ahead in the fifth minute with a drilled shot and should have made it 2-0 from the penalty spot after Gelson Fernandes fouled Jamal Campbell-Ryce moments before the break but missed his attempt.
David Nugent equalised 10 minutes into the second half but a mistake by Sean St Ledger let Maynard in to secure the win with an assured finish.
Brighton made it three wins from three since returning to the second tier after a superb 3-1 victory away to Cardiff.
Gus Poyet's side led through Ashley Barnes' 30-yard strike and a penalty by the same player. Will Hoskins made it 3-0 with the full-time whistle nearing before Peter Whittingham managed to reduce the deficit from the spot in added time.
Derby snatched an unlikely 1-0 win at Blackpool after withstanding the hosts' pressure at Bloomfield Road.
The Rams now also boast a 100% record from three games after Craig Bryson's poached winner against the run of play in the 69th minute.
A lively clash at The New Den saw Millwall lead 2-0 against Peterborough only to end up drawing.
Liam Trotter had put the Lions ahead at the break and Hamer Bouazza made it 2-0, only for the Posh to claw it back through Lee Frecklington and Paul Taylor.