Toulouse were content to keep the pressure on and wait for mistakes, confident that Michalak would extract full punishment with the boot.
The scrum-half kicked his third penalty of the afternoon to allow Toulouse to deny the Blues a losing bonus point, then struck a long-range fifth to leave the visitors needing two scores if they were to take an improbable win.
Gareth Thomas, who earlier in the day had revealed in a national newspaper that he is gay, came off the bench to try and inspire a fight-back.
But despite some encouraging runs against his former club, neither Thomas nor his Blues colleagues were able to find that crucial breakthrough.
The last chance disappeared when having patiently worked their way into range, the Blues spilled the ball and Poitrenaud kicked deep to turn the Welshmen.
The Blues survived a five-metre scrum after Norton-Knight had knocked on trying to gather the awkwardly bouncing ball in his own in-goal area, but gave up another penalty.
Michalak turned the screw again to take his afternoon's tally to 18 points and make Toulouse favourites to top the pool.
Toulouse captain Thierry Dusautoir: "We are satisfied with the result and it was important to win.
"We were disappointed with the defeat in Cardiff last weekend but we are very happy today."
Cardiff Blues director of rugby Dai Young: "We are up against it but we are not dead and buried. We probably have to rely on others to do us favours.
"There are two games left and we want to win those two games.
"It has to be bonus points all the way for us and if we could have got one we could have been in with a shout.
"It is not going to be easy because Sale and Harlequins are two very good sides."
Toulouse: Clement Poitrenaud; Vincent Clerc, Florian Fritz, Yannick Jauzion, Yves Donguy; David Skrela, Frederic Michalak; Jean-Baptiste Poux, William Servat, Benoit Lecouls, Yoann Maestri, Patricio Albacete, Jean Bouilhou, Thierry Dusautoir, Louis Picamoles. Replacements: Virgile Lacombe for Servat (75), Census Johnston for Lecouls (40), Daan Human Poux (50), Shaun Sowerby for Picamoles (58), Romain Millo-Chluski for Maestri (49), Maxime Medard for Poitrenaud (74), Cedric Heymans for Clerc (70), Nicolas Bezy for Skrela (76).
Sin Bin: Albacete (36).
Blues: Ben Blair; Leigh Halfpenny, Tom Shanklin, Jamie Roberts, Richard Mustoe; Sam Norton-Knight, Gareth Cooper; Gethin Jenkins, Gareth Williams, Taufa'ao Filise, Deiniol Jones, Paul Tito (capt), Andy Powell, Martyn Williams, Xavier Rush. Replacements: T Rhys Thomas, Sam Hobbs, Gary Powell, Scott Morgan for Tito (62), Sam Warburton for A. Powell (71), Richie Rees for Cooper (60), Ceri Sweeney for Norton-Knight (77), Gareth Thomas or Mustoe (72).
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