Liverpool vice-captain Jordan Henderson was mysteriously absent from the club's Wednesday morning training session, as they prepare to fly out to Turkey.
They visit Istanbul side Besiktas in the second-leg of their Last 32 Europa League tie, with the Reds holding a 1-0 advantage thanks to Mario Balotelli's late penalty at Anfield last Thursday.
But Brendan Rodgers may have been dealt a blow in his hopes to qualify for the Last 16 tomorrow night, when Henderson was missing from training, suggesting that he'll also be missing the game - but he will await late fitness tests.
The midfielder has been a crucial part of his Liverpool side, playing in all of their last 24 successive games in all competitions - starting all but one, and may have picked up an injury in a 2-0 win over Southampton on Sunday.
Full-time skipper Steven Gerrard, still struggling with a hamstring problem and Mamadou Sakho, who missed the weekend win over Southampton with a hip problem, were also both missing as the squad problems mount up for the Northern Irishman.
With Joe Allen their only recognised midfielder, given that Lucas Leiva is still out for some time, he may be forced into pushing Emre Can into centre midfield and putting Kolo Toure and Dejan Lovren into the back three in the place of the missing Sakho and with Can going forward.
Glen Johnson is another who has been ruled out, with Liverpool's squad depleted by injuries and suspensions.
The Reds take on Slaven Bilic's Besiktas in a sold-out Ataturk Olympic Stadium on Thursday evening.