Howard had to deny Joao Moutinho, while a Yannick Djalo free-kick hit the bar.
Ryan Flynn's close-range strike gave the visitors a 27th-minute lead after a powering run by Pedro Moutinho.
Showunmi skinned Mulgrew before delivering a wicked cross for Moutinho to fire home from close range via the post.
Carl Finnigan struck the equaliser in the dying minutes after Pedro Moutinho set him up with a through ball.
Pressley made three changes for his first home game in the Falkirk dugout, recalling Showunmi, Moutinho and fit-again Vitor Lima.
The visitors opened the scoring when Flynn fired a low strike past John Ruddy in the Motherwell goal after good work from Moutinho.
Joao Moutinho, the first Portuguese player up, saw his shot saved by Iker Casillas, and defender Bruno Alves clanked the fourth kick against the crossbar.
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But the Bairns came roaring back before the break with a cool finish from Pedro Moutinho levelling matters and Darren Barr's header putting them in front.
Sporting gradually increased the pressure and Howard made an instinctive save from Moutinho but could not prevent Veloso from stabbing the ball home from six yards.
Sionko almost had a second goal in the 29th minute when goalkeeper Ricardo flapped at another corner, but Joao Moutinho cleared his header off the line.
Portugal suffered a further blow when Moutinho hobbled off with a knee injury to be replaced by Raul Meireles, but they showed more promise just before halftime.
And the door was firmly closed on Turkey in stoppage time when Ronaldo burst clear on the left, his pass finding Joao Moutinho who set up Meireles to score.
In Group D , Sporting Lisbon maintained their perfect record, with the Portuguese side winning 2-1 away to Latvia's Ventspils thanks to a stunning strike from Joao Moutinho with five minutes left.
The payoff finally came 79 minutes in, when Ronaldo cut in from the left side and dove eight yards from the goal to connect his forehead with a cross from Joao Moutinho.
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Cech leapt and twisted in the 60th minute, sending a hand skyward to deflect over the crossbar a strike from 20 yards by Moutinho that seemed destined for the roof of the net.
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It would have been tough on Everton if their Portuguese opponents had scored from the subsequent opportunity but Sporting skipper Moutinho saw his brilliant strike rebound off the woodwork, while Tonel missed the rebound.
Jose Bosingwa fired in a cross from the left towards Joao Moutinho but it arrived at an awkward height for the Sporting Lisbon midfielder, who diverted the ball over the bar with his thigh.
Miguel Veloso scored direct from a corner in the sixth minute, but Juris Laizans converted a 65th-minute penalty to level before Moutinho crashed a shot into the top corner from a wide position 25 yards out.
The equaliser finally arrived for Falkirk in the dying minutes of a lifeless match after Finnegan picked up a through ball from Moutinho and slotted past Paul Gallacher in the St Mirren goal to snatch a point.
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