Manchester United v Sevilla
Live on BT Sport 2
McTominay needs to stop Banega influencing the game
This match is likely to follow the same tactical pattern of the first leg, with Sevilla holding the majority of possession as Jose Mourinho gradually lures the Spaniards high up the pitch. At Fiorentina, AC Milan, and now Sevilla, Vincenzo Montella relies upon attacking down the flanks via long diagonals into the channels and overlapping full-backs after dominating possession (59% in the Champions League this season). Mourinho, then, will be happy to absorb pressure for the most part.
During the first leg Ever Banega created an incredible 10 chances, many of which were the direct result of long passes into the left channel, an area Sevilla targeted due to the gaps left by Juan Mata on that side. If United are to keep a clean sheet, they will need to limit Banega's influence at Old Trafford.
Scott McTominay is the man who will be tasked with closing Banega down, quickly anticipating those longer passes while also cutting off the passing lines into the Argentine's feet. McTominay was superb against Liverpool last weekend, shuttling across to prevent the visitors from feeding the ball into Roberto Firmino. The 21-year-old will need to be at the top of his game to stop Sevilla feeding the wide areas, stretching United's defence and scoring that crucial away goal.
Sanchez & Rashford can dominate Navas
The flip side of Montella's formation is that Sevilla are vulnerable to counter-attacks down the flanks. United struggled to break consistently in Spain but will be considerably more successful on home soil, not least because they enter this match on the back of three successive wins, culminating in a 2-1 victory over Liverpool defined by fast breakaways down the left.
Alexis Sanchez has been freed from defensive responsibility in his new central role, which not only means he can tackle back against Banega when necessary but also be the fulcrum of the United counter. The Chile international is impossible to track when given a free role; he will look for Marcus Rashford's runs down the left, exposing space behind the opposition right-back.
Rashford easily got the better of Trent Alexander-Arnold at the weekend, and with Miguel Layun ineligible to play he should dominate once again, this time against Jesus Navas. The former Manchester City midfielder isn't positionally good enough to function in this role, meaning Rashford should be able to get the better of him - particularly if Romelu Lukaku drifts over to this side to help the English forward double up on Navas.
Back Man Utd to win and over 1.5 goals at 5/6
Back Marcus Rashford to score any time at 11/5
Barcelona v Chelsea
Live on BT Sport 2
Onus on Fabregas to keep Messi quiet
For Chelsea to stand any chance of qualifying they need Cesc Fabregas to repeat his superb defensive performance against Barcelona in the first leg; without a recognised defensive midfielder to partner N'Golo Kante in the middle, Antonio Conte is relying on Fabregas to shut out the central spaces for Leo Messi.
This is undoubtedly the key battle at the Nou Camp. Fabregas was surprisingly alert in the first leg, shuttling across from within the compact Chelsea shell to deny any space in his zone of the pitch. Consequently, Messi was quiet throughout the match, finding space only once after a couple of errors at the back handed Barcelona their equaliser.
Ernesto Valverde's 4-4-2 formation essentially involves a central midfield square, meaning the central column of the pitch is particularly overloaded with bodies. This is why, with so many other Barca players swirling around this area, Messi can stand still and conjure space; his match-up with Fabregas will be the most difficult encounter of the latter's career. Even a repeat of his showing at Stamford Bridge - itself unlikely - probably won't be good enough on Messi's home ground.
Giroud needs to bully Umtiti
Conte played Eden Hazard as a false nine during the first leg, but surely he will restore a target man to the first 11 for this difficult away tie. Without Olivier Giroud (or, though less likely, Alvaro Morata) up front, Chelsea will struggle to turn their clearances into counter-attacking opportunities.
They need someone who can hold the ball up, buying time for the wing-backs to bomb forward and provide support, or else Barcelona will carry out wave after wave of attack, grinding the Premier League holders into submission. Assuming Giroud starts, then, his main battle will be with Samuel Umtiti.
Giroud will presumably look to avoid confronting the stronger of the two centre-backs, Gerard Pique, and instead move onto the left centre-back. Umtiti isn't as good in the air as Giroud, which should mean his France team-mate has the upper hand when Chelsea launch long balls towards their new striker. It might seem like an innocuous battle on the surface, but unless Giroud bullies the Barcelona back line - something he rarely achieved as an Arsenal player - Chelsea don't stand a chance.
Back Barcelona to win with a -1 handicap at 6/5
Back Messi to score two or more at 3/1