Manchester United host Barcelona at Old Trafford tonight in a fixture that was once a Champions League final but is now a Europa League play-off for the round of 16.

That is an indication of the two club’s respective declines in recent years, although the future looks brighter for both this season.

With a place in the last 16 of the competition up for grabs, here are three reasons to watch the first leg, live on BT Sport 2 and Ultimate.

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Another clash of the titans

In what was once a regular fixture in the Champions League knockout stages, Manchester United are midway through a battle for the round of 16 in the Europa League.

Yet there was no sense of a lack of prestige last Thursday when the two European giants battled it out in a 2-2 draw.

Marcos Alonso gave the hosts the lead early in the second half but in the space of seven minutes Man United turned the tie on it's head through Marcus Rashford and Jules Kounde's subsequent own goal.

Man United and Barcelona do battle again on Thursday.

But Raphina's goal 14 minutes from time for La Liga's leaders ensured Barcelona go back to Manchester on level terms in a tie that's balanced on a knife edge.

In a largely even game in Catalonia, it'll be fascinating to see if the Theatre of Dreams has a role to play on Thursday night and if the home crowd will provide the edge Man United need to get over the line.

Will Barcelona make it a miserable evening for Erik ten Hag's men and advance to the last 16? Or will Man United evoke the spirit of 2009 and knock out the Spanish giants?

Will Rashford continue his hot streak?

There are few players in Europe on better form in front of goal than Manchester United forward Marcus Rashford.

Since returning from the Qatar World Cup, Rashford has netted 16 times in 17 games in all competitions at club level.

The England striker's brace against Leicester on Sunday was Rashford's fifth and sixth goal in five matches and that run includes his strike last Thursday at the Camp Nou.

Marcus Rashford
Marcus Rashford is in fine form.

The 25-year-old squeezed Man United's equaliser in from a tight angle last Thursday and Rashford will once again be key to the Premier League giant's chances of coming out on top at Old Trafford.

One of the best in the competition, Erik ten Hag will be hoping his star man can leave an indelible mark on the competition.

Can Barcelona bring their league form into Europe?

Top of La Liga by eight points, seven wins from seven league games and just one loss and two draws from 22 games... it's been a brilliant campaign so far for Xavi's Barcelona.

Summer signing Robert Lewandowski has hit the ground running with 15 goals in 19 appearances while youngsters Gavi and Pedri - before his injury - have been outstanding in midfield.

Barcelona also defeated rivals Real Madrid in the Spanish Super Cup - live on BT Sport - to win Xavi his first trophy as the club's manager.

Xavi has led Barcelona to top of La Liga.

Now the Barcelona legend, with his side looking set to return to the Champions League next term, will be hoping he can make some serious progress in European competition.

A win over Man United and a place in the Europa League round of 16 would be the start of that and surely solidify the Spaniards as one of the favourites for the trophy.