The beauty of Tevez's 10th goal of the campaign, a neat finish after Cristiano Ronaldo had returned the Argentine's overhead kick with a impish back-heel, was at odds with the fractured nature of the contest. But, as Tevez also hit the post on two occasions, United were worthy of a 10th successive home win, although the sight of the already-substituted Argentina striker needing to be carried to the dressing room by two members of United's backroom staff after the final whistle was not what Sir Alex Ferguson would have wanted to see. Handed his first start since March, Park Ji-sung worked predictably hard, as did Nani on the left flank. But equally predictably, it was largely left to Ronaldo and Tevez to test Birmingham's defence.
Tevez might have put the hosts ahead in the opening stages when he rose to meet Patrice Evra's near-post cross. Instead, the South American powered his header against the foot of Maik Taylor's right-hand post, meaning United were forced to endure another 20 minutes of frustration before they eventually made their breakthrough.
After finding Ronaldo with an overhead kick, Tevez continued his run, collecting an inspired back-heeled return pass inside the Birmingham box before beating Taylor in a manner that looked far easier than it actually was, before celebrating in bizarre fashion, pulling a dummy out of his pocket and sticking it in his mouth.
Ferguson, completing a two-match touchline ban, must have been dismayed at his side's inability to capitalise on their advantage. Had Gary McSheffrey showed a bit more calmness, he could easily have levelled with an angled drive, while Sebastian Larsson curled a free-kick straight at Tomasz Kuszczak in stoppage time.
Birmingham could only have gained more heart from surviving more United pressure at the start of the second period, when Tevez struck the post for a second time. What the former Boca Juniors player lacks in size he more than makes up for in determination and after muscling his way on to Park's pass, Tevez deserved more than to see his 10-yard effort cannon back off the woodwork.
Tevez certainly deserved the standing ovation he received when he was replaced by Louis Saha 19 minutes from time, but it must have been slightly frustrating his efforts had not wrapped up the points before his exit.
Birmingham promptly enjoyed their best spell of the game, with former Chelsea man Mikael Forssell causing some anxiety within home ranks when he drifted a low shot just wide, but United held on.