(Adds Guardiola quotes)
DONETSK, Ukraine Oct 1 (Reuters) - Lionel Messi scored twice in the final minutes to give Barcelona an unlikely 2-1 win away to Shakhtar Donetsk in their Champions League Group C match on Wednesday.
The Argentine equalised in the 87th minute then scored a brilliant chipped winner four minutes into stoppage time after Barca had looked on their way to defeat.
"We already know what Messi is capable of doing," a happy Barcelona coach Pep Guardiola was quoted as saying by Marca.
"Leo does the unexpected and is a very decisive player."
Barcelona lead the group with six points from two matches. Sporting, who beat Basel 2-0 in Lisbon, are equal with Shakhtar on three points and the Swiss side have none.
Brazilian winger Ilsinho put Shakhtar ahead in the last minute of the first half when he ran on to Gerard Pique's poor attempt at a headed clearance, slipped between two defenders inside the box and confidently chipped over Victor Valdes.
Shakhtar had the better of the second half but a blunder by goalkeeper Andriy Pyatov in the 87th minute allowed the Spanish giants, who had lacked inspiration or penetration, back into the game.
Young Barcelona substitute forwards Messi and Bojan Krkic, who had come on for Thierry Henry and Samuel Eto'o, combined for the equaliser. Bojan crossed from deep on the right, Pyatov spilt the ball and Messi pounced to put it in the net.
Eto'o should have equalised shortly after the hour when he was put through by Messi but stumbled as he shaped to finish and placed the ball wide of the near post.
Shakhtar's Croatian captain Darijo Srna could have put the Ukrainian team two up in the 77th minute but his fierce shot from the right after a corner was parried away by Valdes.
The unimpressive Henry was replaced by Messi in the 60th minute after just one notable attempt at goal, a close shot saved instinctively by Pyatov.
The result will be a huge disappointment for Shakhtar, who started their group campaign with a 2-1 win away to Basel and had beaten Barca 2-0 the previous time the teams met in Donetsk in December 2004. Defeat adds to the woes of the Ukrainian champions who are a lowly 11th in the domestic league. (Reporting by Sabina Zawadzki, editing by Rex Gowar)