Estimated read time: 4-5 minutes
BARCELONA, Spain (AP) — The Champions League returns Tuesday and Wednesday with Cristiano Ronaldo and Lionel Messi competing for yet another prize as the rival stars take aim at the tournament's all-time scoring record.
While the world's top two players continue their individual battle, three of England's four teams seek their first win, and the Spanish and Italian champions clash this week in Europe's top-tier competition.
Here are the things to know about this week's Champions League group games:
Ronaldo and Messi are neck-and-neck in a race to become the Champions League's all-time leading scorer by breaking the record held by Raul Gonzalez.
Ronaldo has 68 goals in Europe's top club competition, one more than Messi. Raul scored 71.
Ronaldo may have a better chance of getting there first as Real Madrid plays at Bulgaria's Ludogorets in Group B on Wednesday, a day after Messi's Barcelona has a tougher trip to Paris Saint-Germain in Group F.
The Portugal forward looks primed to increase his goal haul in Sofia after scoring 10 goals in his last six matches, including one four-goal performance and a hat trick.
Messi, meanwhile, scored his 400th and 401st goals for club and country in Barcelona's 6-0 rout of Granada on Saturday.
Their latest two-man contest comes after they have divvied up the Ballon d'Or for the world's best player for the past six years and have taken turns leading the Champions League in scoring for the past seven seasons.
PSG not only has the problem of stopping Messi. It may have to do so without striker Zlatan Ibrahimovic.
When Ibrahimovic has been sidelined, the team has won only 40 percent of its matches. And coach Laurent Blanc is sweating on his fitness after Ibrahimovic missed the last two games because of a left heel injury.
"I don't know which attacking players I will have available against Barcelona," Blanc said. "We don't play the same way when Ibra's here and when he isn't. For the time being there is still a question mark. The medical staff will do everything to try and heal him."
ENGLISH NEED TO WIN
Liverpool was the only English team to open the Champions League with a win, and only with a last-gasp goal against newcomer Ludogorets. Basel will present a far tougher challenge on Wednesday with striker Daniel Sturridge out injured as Liverpool looks to keep pace with Madrid in Group B.
Chelsea's reliance on Diego Costa for goals seemed clear when the striker sat out the 1-1 draw against Schalke in the Group G opener. And ongoing problems with Costa's left thigh are likely to force him to miss Tuesday's game at Sporting Lisbon.
"He's doing almost nothing (in training)," Chelsea manager Jose Mourinho said. "He's just resting and recovering from the tight muscle he has. Every time he accumulates fatigue."
Mourinho, who worked at Sporting as assistant to Bobby Robson between 1992 and 1993, is out to end Sporting's 16-match unbeaten home run in Europe.
Manchester City faces a formidable test Tuesday with the visit of a Roma side which has made a perfect start to the season at home and in Europe. It's been a patchy beginning to the campaign for City, which opened Group E with a loss at Bayern Munich.
In Group D, Arsenal hosts Galatasaray on Wednesday with both Mikel Arteta and Aaron Ramsey out injured.
RUNNER-UP AT RISK
Atletico Madrid was minutes away from winning the European Cup last May before the title slipped away to Madrid.
Now after losing this season's opener, the Spanish league champions face a crucial game on Wednesday when Serie A champion Juventus comes to town.
A loss to Juventus, combined with an Olympiakos win at Swedish side Malmo, would leave Atletico six points adrift in Group A.
Atletico will be boosted by the return of coach Diego Simeone to the sidelines after he missed the first game due to suspension.
XABI TAKES CONTROL
Bayern travels to CSKA Moscow on Tuesday in Group E with midfielder Xabi Alonso firmly in control of his new team.
The Spaniard was only signed at the end of the transfer period after several players went down with long-term injuries.
But Alonso stepped right in and has been impressive in directing Bayern's attack.
On Saturday, Alonso set a Bundesliga record by touching the ball 206 times in a 2-0 win at Cologne.
AP writers Rob Harris in London, Jerome Pugmire in Paris, and Nesha Starcevic in Berlin contributed to this report.