Just a month into the season, Manchester City is already facing a game of huge significance in the defense of its Premier League title.
If City loses at home to early leader Chelsea on Sunday, the champions will be eight points behind their biggest rivals for the championship after five matches.  And that will be a sizeable gap considering the strength of the squad that Jose Mourinho has built for this season.
Buoyed by a 4-0 win over Queens Park Rangers last weekend, Manchester United's line-up of all star attackers heads to another promoted club, Leicester, with Radamel Falcao in line for a first start.
And second-place Aston Villa, the surprise of the season, looks to maintain its unbeaten start when it hosts Arsenal.
Here are some things to know about the
upcoming round of games:
CITY BLUES?
Man City's start to the season is giving ammunition to the critics who questioned whether the club's offseason recruitment was good enough.
While most of its rivals brought in exciting attacking talents for the new season, City chose to bolster its squad with extra defenders and a tough-tackling defensive midfielder in Fernando - purchases that were sensible but hardly set the pulses racing. The champions are also down to three strikers after selling Alvaro Negredo on the final day of the transfer window.
City's 1-0 loss to Bayern Munich in the Champions League on Wednesday extended its winless run to three games ahead of the visit of Chelsea, which did the double over City last season.
Some early-season pressure would come on City
manager Manuel Pellegrini if he fails to mastermind a victory over Mourinho, whose tactics were perfect in Chelsea's 1-0 win at Etihad Stadium in February.
COSTA RELIANCE
If there's any glimmer of hope among Chelsea's rivals after the London club's superb start to the season, it's Mourinho's reliance on Diego Costa.
Costa has scored seven goals in four straight wins for Chelsea to open the league season, despite being hampered by hamstring problems.
The Spain striker was only a substitute, though, in Chelsea's opening Champions League game - a 1-1 draw at home to Schalke on Wednesday, with Mourinho saying Costa is only fit enough to start one match per week.
"It was not to protect Costa for the game on Sunday," Mourinho said, "it was because he was not in condition to start the game." WILL FALCAO START?
Given an extra week to acclimatize following his high-profile loan move from Monaco, Radamel Falcao should be ready to start for Man United at Leicester as Louis van Gaal's side look for a second straight win.
Falcao came on as a 67th-minute substitute for Juan Mata against QPR, partnering Robin van Persie up front with Wayne Rooney dropping back into the No 10 role. That could be the attacking formation Van Gaal goes with in future. Van Gaal must also decide whether to stick with a four-man defense that seemed to work better against QPR than a 3-5-2 had done in United's opening three games in the league, when it gained just two points.
SURPRISING VILLA, SWANSEA
There's usually one team that pops up near the top of the standings for the first weeks of the season before typically falling away.
This season, there are two sides who have made surprising starts.
Aston Villa has picked up 10 points from a possible 12, with its third win of the campaign coming at Liverpool on Sunday. The reward for manager Paul Lambert was a new contract on Wednesday through the summer of 2018.
Villa, which battled to avoid relegation last season, is in the middle of a tough run of fixtures that will test its resurgence, with the home match against Arsenal followed by games against Chelsea, Man City and Everton.
Swansea is the other unlikely member of the current top four, with its run of three straight wins ended by Chelsea last week despite an encouraging performance at Stamford Bridge.
Swansea is at home to Southampton.
BALOTELLI WARNING
Scoring goals may not be enough for Mario Balotelli to be the new crowd favourite at Liverpool.
The Italy striker ended his wait for a goal for his new club by scoring in Tuesday's 2-1 win over Ludogorets Razgrad in the Champions League. But manager Brendan Rodgers says Balotelli must dovetail scoring with a relentless work rate, like Luis Suarez did during his turbulent 3½ years at Anfield.
"You can see that he's trying to put himself in for the team - and that's going to be very important, because the crowd demand that," Rodgers said of Balotelli. "The players that have been here in the past in that position, they've been non-stop, and he's becoming attuned.
"He's putting his body on the line, and he needs to do more.
" With Daniel Sturridge still out injured, Balotelli should again lead Liverpool's attack against West Ham.