Pep Guardiola's side, bidding to become the first team to successfully defend the Champions League trophy in its current format, looked anything like holders in a first-half dominated by the Germans.
It was wave after wave of Stuttgart attack as the visitors struggled to find anything like their rhythmic, fluent best - even the usually reliable Andres Iniesta was giving the ball away with alarming regularity.
Cristian Molinaro, on the other hand, was enjoying the time of his life down the Stuttgart left as he tormented Barca captain Carles Puyol, standing in for the injured Daniel Alves.
Molinaro raced past Puyol time after time, Cacau mis-hitting a shot from one of his crosses and then Timo Gebhart miscuing a header from another, with the Barca defence at sixes and sevens.
But the Germans soon had the lead their dominance deserved. Gebhart whipped over a fine cross from the right and Cacau slipped Puyol at the back post to thump a header past Valdes.
Barca were in danger of being over-run and Pavel Pogrebnyak was only denied a shooting chance by a well-timed last-ditch block from Puyol before Cacau's toe-poke forced a fine save from Valdes.
Gradually, as half-time approached, Barca seem to wake from their slumber. Messi had been quiet, but suddenly he burst into life with one solo run and shot that ended with a clumsy tip against the post by Lehmann.
Ibrahimovic celebrates his equaliser for Barcelona
When they came back out for the second half, Barcelona took only seven minutes to get themselves back on level terms.
A cross into the Stuttgart box was flicked on and Gerard Pique was on hand to head the ball down to Ibrahimovic. The Swede's first shot was superbly saved by Lehmann, but he had plenty of time to slot in from the rebound.
All of a sudden, Barca were revitalised. Thierry Henry came on for Yaya Toure as Iniesta dropped back to link up with Xavi in midfield and Messi almost fashioned a goal with a mazy run from the right that required some brave Stuttgart defending to clear.
After Sami Khedira dragged wide in a rare Stuttgart attack, Lehmann almost gifted Barca the lead in the match.
He came for a corner and completely missed it, Ibrahimovic turning superbly to rifle in a volley that seemed to hit Molinaro on the arm before deflecting over the bar.
Barca passed the ball around in the closing stages as though the tie was already won; Christian Gross and Stuttgart will hope they are left rueing their complacency on 17 March.
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