The former Everton flop Ibrahima Bakayoko helped bring Blackburn's 15-match unbeaten run crashing to an end and leave them on the brink of Uefa Cup elimination at the first hurdle.
Bakayoko and Brazilian Cleyton scored two goals in 90 disastrous first-half seconds as the Greek Cup winners pulled off a shock first-round, first-leg result.
The defeat, Rovers' first since 15 April, leaves manager Mark Hughes' side facing an uphill task in the second leg at Ewood Park in a fortnight. Hughes and his players had talked promisingly before the match of potentially going all the way in the competition, but that now appears a forlorn hope.
For half an hour Rovers appeared comfortable as Larissa barely posed a threat, but then Blackburn hardly put their opponents under pressure either.
Their ease was aided by the fact there was none of the 30 degree Celsius heat as had been prevalent earlier in the day, and the game was being staged at the Panthessaliko Stadium 40 miles away from Larissa's own Alkazar Stadium which does not meet Uefa standards.
Blackburn's best opportunity of a wretched match arrived in the 19th minute. A long throw from Morten Gamst Pedersen was taken on the chest by Benni McCarthy on the edge of the six-yard area.In one movement McCarthy swivelled onto the ball, striking a volley goalwards that smacked German defender Marco Foerster in the face.
Then came those 90 miserable seconds as Rovers found themselves two goals adrift and staring at an unlikely early exit from the competition.
Bakayoko's strike was a touch fortunate as the 30-year-old let fly from 30 yards only for his shot to take a slight deflection off Ryan Nelsen. But that was enough to help beat Brad Friedel, who was standing on the edge of his six-yard box, as he could do nothing but paw at thin air as the ball flew over him and into the roof of the net.
Moments later further trouble followed, this time courtesy of Blackburn's own making, and in particular a woeful back pass from just inside his own half from Brett Emerton.
Seizing onto the underhit ball, Nektarios Alexandrou was initially denied by a spread-eagled Friedel, while Andre Ooijer then blocked Bakayoko on the rebound. The loose ball ran to Giorgos Fotakis who teed up Cleyton and the Brazilian delightfully curled home a fine second from 12 yards.
A clawing save from Friedel from Fotakis' 20-yard free-kick denied Blackburn further embarrassment at the start of a second half in which they were distinctly second best.
The loss of captain Nelsen just before the hour added to Rovers' woes, forcing them onto the backfoot as last-ditch defending on occasions became the order of the day. Despite four minutes of injury time, Rovers failed to conjure an away goal that could have aided their cause, and now it is all or nothing in two weeks' time in the return leg.
Larissa: Kotsolis, Foerster, Katsiaros, Dabizas, Galitsios, Kiriakidis, Cleyton, Sarmiento, Fotakis, Alexandrou, Bakayoko. Subs: Kipouros, Gikas, Kalantzis, Venetis, Boukouvalas, Bahramis, Kozlej.
Blackburn: Friedel, Ooijer, Warnock, Nelsen, Emerton, Savage, Bentley, Pedersen, Dunn, Santa Cruz, McCarthy. Subs: Brown, Khizanishvili, Mokoena, Derbyshire, Olsson, Roberts, Kerimoglu.
Referee: P Sippel (Germany).Reuse content