AC Milan and Ajax will play for a spot in the knockout stage of the Champions League on Wednesday.
Milan needs only a point at San Siro, while Ajax has to win the Group H match.
Barcelona can assure itself of first place in the group with a draw against Celtic.
Here are five things to know ahead of Wednesday's matches:
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BALOTELLI'S BACK
After a difficult few months for Mario Balotelli, the AC Milan forward is now showing signs he is back to his best.
Balotelli scored twice in Saturday's 2-2 draw against Livorno in Serie A to take his tally to four goals in his past three matches for Milan and snapping a run of eight matches for club and country in which he had failed to find the back of the net.
The 23-year-old Balotelli, who has already been suspended twice this season, has scored six goals in 10 league matches as well as three in the Champions League.
Balotelli's return to form comes at an opportune time for Milan, which is languishing in eighth place in the league after only one win in seven matches.
''We know exactly what type of footballer Balotelli is,'' Milan teammate Sulley Muntari said. ''We know how he can help us, we know his strenghth and his ability on the pitch. When Mario wants to, he knows how to be decisive in matches, he's like Ibra (Zlatan Ibrahimovic). Balotelli is exactly in that category, things depend on him. When Mario decides to do well, he always does well.''
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KAKA'S 100
Kaka continues to impress at AC Milan after rejoining the club at the start of the season following a difficult four years at Real Madrid.
The Brazilian has found the back of the net four times this season and has now scored 99 goals in his two spells at Milan.
''I really feel that the Milan shirt is like a second skin for me,'' Kaka said. ''I dreamed of wearing this shirt and I hope to do so for many more years. I missed the atmosphere of Milan's training ground, the history of the club. I had a great but difficult time at Madrid.
''I hope to score my 100th goal as soon as possible and it would be nice to make that mark against Ajax.''
Kaka played against Ajax four times in his past two seasons at Real Madrid. He scored at the Bernabeu as Madrid beat Ajax 4-1 both home and away last year and was also on target the previous season when the Spanish team won 3-0 both home and away.
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READY TO ATTACK
Ajax managed to hand Barcelona its first defeat of the season two weeks ago even without its first-choice strikers.
The 2-1 victory set up Wednesday's decider against AC Milan for the second qualifying berth from Group H. Ajax has to win to progress while a draw would be enough for Milan.
Ajax captain Siem de Jong is still sidelined with injury, but Iceland striker Kolbeinn Sigthorsson is fit again after recovering from an ankle injury and so is former Milan striker Bojan Krkic, who has scored in his last two matches coming off the bench.
Danny Hoesen, who scored Ajax's second in the win over already-qualified Barcelona, is also in Frank de Boer's squad for Wednesday's match at San Siro.
But the man most in form in front of goal for Ajax is 20-year-old midfielder Davy Klaassen, who scored a hat trick on Saturday in the 4-0 win over NAC Breda.
Klaassen is in the form of his life after coming back from a groin injury that sidelined him for nearly an entire season. Klaassen is so highly rated in Amsterdam that even Ajax great Johan Cruyff took an interest in his recovery, getting him specialist treatment in Barcelona.
Now Klaassen believes the must-win match against AC Milan will be an advantage for the attacking-minded Ajax.
''We have to win and maybe that's good. That suits us,'' Klaassen said.
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BARCELONA BLUES
Barcelona's ability to clinch its group with games to spare is proving beneficial with the Spanish champions dealing with injuries and grumpy players.
Lionel Messi is out for a few more weeks while Andres Iniesta, Xavi Hernandez and Dani Alves continue to recover from knocks that kept them out of Friday's 4-1 Copa del Rey win at third-tier club Cartagena.
That victory ended a two-game losing run, but the mood has not been rosy.
Young defenders Marc Montoya and Marc Bartra, plus winger Cristian Tello, have spoken of needing more playing time. Midfielder Alex Song has been rarely used, and the club is even having trouble hanging on to youth prospects, such as Paraguay striker Tonny Sanabria.
Former midfielder Thiago Alcantara recently said moving to Bayern Munich was ''the best decision of my life.''
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FAN FOCUS
Celtic's trip to Barcelona is a chance for fans of the Scottish champions to repair their battered reputation.
Violence against Ajax fans in Amsterdam last month led to five Celtic fans being convicted. And bad behavior marred Celtic's league match against Motherwell on Friday.
Celtic has suspended 128 fans from their games as a result of the disorder. Smoke bombs and flares were thrown, while seats were damaged.
''You don't want to have mayhem, you can't have this disruption inside sports grounds so we have to get together to support the club in the best way,'' Celtic assistant manager Johan Mjallby said Tuesday. ''It is a distraction I don't like to see because I like to work with the players.''
