It could have been much worse though. After 65 minutes Boro's European adventure looked to be over as they trailed by three goals and lacked penetration.
A late two-goal fightback made the scoreline respectable. The question is - can it inspire them to pull off a shock win in the second leg in Portugal next week?
In the match programme Middlesbrough manager Steve McClaren called for "a superlative performance" against one of the best technical sides in Europe.
His players, however, failed to respond until the final stages after the visitors had strolled in to what had appeared to be a commanding lead.
In a goalless first half, there was controlled football but limited thrills, with Boro waiting 40 minutes for their first shot on target.
However, the visitors began the second half with a two-goal, five-minute burst.
Barbosa gave Mark Schwarzer no chance with his shot and Liedson followed up with a close-range tap-in at the far post.
The crowd tried to lift Middlesbrough but they must have felt the game was all over when Douala increased the lead after 65 minutes.
Substitute Joseph-Desire Job, who had taken over from Daniel Graham, scored with a spectacular overhead kick 11 minutes from time to inspire the fightback.
Job gave Ricardo no chance with a shot into the roof of the net from a free-kick by Bolo Zenden.
Schwarzer denied the visitors with a brilliant save before central defender Chris Riggott cashed in on a goalkeeping mistake at the other end.
When Ricardo dropped the ball Riggott finally shot from just inside the penalty area.
Lisbon were worthy winners on the night and will start strong favourites to reach the quarter-finals.
It would be a dream for Sporting to go all the way because the Portuguese club stage the final in May.
Middlesbrough will not throw the towel in but it will take a Herculean effort to stay in the competition.