Foster kept the score down and Birmingham out of the relegation zone with a string of saves, denying Sidwell, Clint Dempsey and Johnson.
Owens fired over at the backpost in the first period of extra-time before O'Neill produced two excellent saves, denying McMullan and Boyce.
The Canaries' England international goalkeeper Ruddy was forced into a series of impressive close-range saves, denying Ricardo Vaz Te, Cole and Kevin Nolan in the space of eight first-half minutes.
Kenny kept Leeds in sight of a point with two more fine saves, denying Maynard from six yards and then dropping to the ground quickly as Smith fired from 18 yards through a crowded area.
That instigated a better spell for Allardyce's side, who almost went in front again, but Elliot's superb double save denied Nolan, while Carroll had another penalty appeal turned away by referee Phil Dowd.
And boomers, better known for spending than saving, deny themselves little -- even if it means going into debt.
The 53-year-old could do nothing as star striker Lotta Schelin and team-mate Kosovare Asllani both had second-half penalties saved, denying the team a perfect start to their campaign.
The most inviting chance of the first half was the one for Jake Livermore, after 11 minutes, when David de Gea's one-handed save denied him beneath the Stretford End.
The save denied Blackburn a 22nd-minute lead, after which Leicester – perhaps inspired – won comfortably, first-half headers from Chris Wood and on-loan Harry Kane supplemented by a third in stoppage time by Andy King.
But his Hollywood moment came in the second half when his double save denied Fletcher and Hammill.
