Southampton and Birmingham, two sides expected to occupy the Premiership's middle ground this season, fought out a tough battle at St Mary's with the Saints marginally the better in the first half but Birmingham unlucky not to win.
Only a superb save by Paul Jones in the 87th minute denied substitute Clinton Morrison a goal, which would have sealed Birmingham's recovery from a tentative start.
Saints should have been firmly ahead by the interval with Michael Svensson heading wide of an open goal from 12 yards and James Beattie hitting the post with a left foot shot.
New signing Kevin Phillips went close with a header but Birmingham took control. Stern John had a header cleared off the line by Graeme Le Saux while Geoff Horsfield wasted two clear openings.
Stephen Clemence hit the post from a Robbie Savage free kick as Savage and David Dunn ran the midfield for the Blues.
Southampton failed to make a clear opening after the break to the worry of manager Gordon Strachan. Beattie and Phillips struggled to get the better of Matthew Upson and Kenny Cunningham as Birmingham assumed a strong grip.
Saints had three players booked including Le Saux but the turning point came in the 71st minute. Dunn, cutting in from the right, stumbled under a challenge from Le Saux and then fell but referee Graham Barber, who was close to the incident, waved play on as the stadium fell silent.
Le Saux was booked in the 10th minute for a foul on Damien Johnson and was twice more involved in incidents which might have led to his sending off including what appeared to be an elbow on the irrepressible Savage.
Claus Lundekvam and Fabrice Fernandes were also cautioned for fouls while Savage marred an impressive midfield performance of dynamic running and tackling by earning a yellow card in the 78th minute, also for a foul.