A look at what's happening in the Europa League in some of the first legs of the last 16 on Thursday: 

OLYMPIAKOS VS. ARSENAL

Sokratis Papastathopoulos is back facing Arsenal less than two months after joining the Greek champions. Having been left out of the squads for both the Premier League and Europa League, the defender did not feature for Arsenal at all during the first half of the current season. Olympiakos shocked Arsenal at the round of 32 last season. Arsenal could have Emile Smith Rowe available after the attacking midfielder picked up a muscular injury in the recent win at Leicester and missed Saturday's draw at Burnley. Arsenal manager Mikel Arteta has no other injury concerns but does have Sunday's north London derby at home to Tottenham to consider when picking his team in Athens.

MAN UNITED VS. AC MILAN

Manchester United manager Ole Gunnar Solskjaer does not expect forwards Marcus Rashford and Edinson Cavani to have fully recovered to face AC Milan. It will be the first meeting in 11 years between the two clubs steeped in European tradition and both have slipped from the pedestals they once occupied. Milan won the Champions League in 2007 and United picked up the European Cup the following year but now they are competing for the continent's second-tier trophy. Both are well-placed to qualify for the Champions League next season as they are second in their domestic leagues. 

TOTTENHAM VS. DINAMO ZAGREB

Tottenham has a League Cup final against Manchester City to look forward to in April, while the London club continues its Europa League quest against Dinamo Zagreb as its looks to end a title drought stretching back to 2008. Winning the Europa League could be the only way back into the Champions League next season. Jose Mourinho's side is five points behind fourth-place Chelsea. Dinamo arrives in London in good form with eight consecutive wins in all competitions.

SLAVIA PRAGUE VS. RANGERS

Rangers sealed its first Scottish title in 10 years on Sunday and now turns its attention to trying to add a European trophy. But Slavia Prague knocked out Premier League top-four contender Leicester in the previous round.

THE REST

It's Ajax (Netherlands) vs. Young Boys (Switzerland), Dynamo Kyiv (Ukraine) vs. Villarreal (Spain), Roma (Italy) vs. Shakhtar Donetsk (Ukraine) and Granada (Spain) vs. Molde (Norway)