What to watch out for in the Champions League

Cristiano Ronaldo, Diego Costa and André Schürrle will be out to keep the goals flowing in the round of 16 deciders as UEFA.com identifies the second legs' key flashpoints.

Cristiano Ronaldo added four more goals to his season total on Saturday
Cristiano Ronaldo added four more goals to his season total on Saturday ©AFP/Getty Images

How many will Ronaldo score?
Already 2-0 down, Roma need no reminding of Cristiano Ronaldo's class, but the Real Madrid No7 issued one anyway by scoring four in Saturday's 7-1 thrashing of Celta Vigo to go second in the all-time Liga scoring charts and top of the Liga standings for this season on 27 – one above Barcelona's Luis Suárez. The Portugal forward also leads the way in the 2015/16 UEFA Champions League on 12 goals, his record 11 group-stage strikes followed by another first-leg effort against Roma as he moved onto 88 in the competition – another record.

Cristiano Ronaldo v Roma
Cristiano Ronaldo v Roma

Recently-appointed Roma coach Luciano Spalletti, however, hopes Mohamed Salah and Stephan El Shaarawy can combine to upstage Ronaldo, saying after Friday's 4-1 win against Fiorentina: "If we can give them the ball quickly from midfield, El Shaarawy and Salah can be devastating." El Shaarawy has registered five goals in six Serie A games since joining from Monaco, while Salah has five goals in his last four league outings – statistics that suggest there is fight left in Roma yet.
Real Madrid v Roma, Tuesday

Wolfsburg's Schürrle finding form? 
André Schürrle went into last Tuesday's fixture at Hannover with two goals in 33 Bundesliga appearances for Wolfsburg – figures hardly consistent with the reported €32m transfer fee paid to Chelsea for the forward in January 2015. A 27-minute hat-trick in that 4-0 success, however, has given him a huge lift. "A lot has been written, a lot has been said," Schürrle explained. "I think I just gave the right answer." Not that he was entirely satisfied, noting: "I am annoyed – I should have had four."

Highlights: Gent 2-3 Wolfsburg
Highlights: Gent 2-3 Wolfsburg

That impatience augurs well for the decider against Gent; the Wolves won the away leg 3-2 and the Belgian champions' coach Hein Vanhaezebrouck has given his team a "zero per cent" chance of reaching the last eight. He did say the German side might "start to panic" if they conceded the first goal, but added: "I still think they have more class. But we won't give up and I expect my players to prove me wrong."
Wolfsburg v Gent, Tuesday

Time for Costa to come good
The first-leg loss in Paris remains Chelsea's only defeat in 16 matches under Guus Hiddink this term, and the stand-in manager wants the west Londoners to bare their teeth in the home return. "We will need to be angry from the start on Wednesday, but in a controlled way," he said. "We are playing a class team and they will punish you if you start sloppy." Paris have not won in two Ligue 1 outings – their worst run of the campaign – but felt secure enough at the top of the table to give 18-year-old midfielder Christopher Nkunku his debut and play Presnel Kimpembe, 20, at centre-back in Saturday's 0-0 draw with Montpellier.

Highlights: Paris 2-1 Chelsea
Highlights: Paris 2-1 Chelsea

Diego Costa may be the man to watch for Chelsea; the Spanish international has plundered ten goals since Hiddink's arrival having managed just four in 2015/16 before the Dutchman's appointment. The UEFA Champions League has been a goalscoring blind spot of late – having hit eight for Atlético Madrid en route to the 2014 final, Costa has notched only once in 14 European appearances for Chelsea.
Chelsea v Paris, Wednesday

Zenit firing on all cylinders
The 1-0 first-leg reverse at Benfica was perhaps no disaster for Zenit, given it was their first game of the year. Now further sharpened by an extra-time Russian Cup triumph against Kuban and an underwhelming 0-0 draw at Krasnodar in their first Premier-Liga fixture of 2016, midfielder Danny reckons his side are up to speed. "We have increased our confidence and tempo and we are ready, 100%," he noted. "Benfica are a top-quality team but we are strong, we are at home and we want to win."

They can only hope Benfica are a little distracted following Saturday's 1-0 derby success at Sporting CP – a result that put the Portuguese champions top of the Liga outright for the first time since the opening day of the season. "We're happy, but there are still nine finals left," coach Rui Vitória said. 
Zenit v Benfica, Wednesday

All kick-off times CET