Premier League Spotlight previews the weekend's top-flight fixtures, highlighting the key points to keep an eye on as the action unfolds. Under the microscope this week: a response required from Arsenal, question marks over John Terry's partner, a chink in Liverpool's armour, Luka Modric's head and penalty takers.

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Arsenal: The walking wounded

They had to feature, simply had to. It is now four self-inflicted Premier League Spotlight editions running for Arsenal. This column wrote pre the visit to Old Trafford, post the Udinese result: "The glaring weaknesses still remain, and the Gunners could do without a trip to champions Manchester United with their squad in the state it's in at present."

There was some anger in the comments section at the suggestion a crisis could be around the corner. Then the 8-2 loss followed. Arsene Wenger has reacted, though there is conjecture over whether he would have signed Andre Santos, Per Mertesacker, Mikel Arteta and Yossi Benayoun had his depleted squad not committed footballing suicide at Old Trafford. Regardless, the Frenchman's crop has swelled, and now they must respond versus Swansea City.

But even when Arsenal look to be climbing out of the dark, an inevitable injury or two brings back the depression. Their key midfielder Jack Wilshere - key at 19 years old - is set for another two months on the sidelines while influential defender Thomas Vermaelen, who made just two league appearances in the last campaign due to an Achilles issue, has gone under the knife following the discovery of a problem with his right ankle. These setbacks aside, even Arsenal should have enough to see off Swansea at home, with the newly-promoted club still awaiting their first ever Premier League goal. Oh, but then another caveat: the Gunners have taken just 13 points from their last 14 league matches. That is wretched form.

To even draw at Emirates Stadium against the Swans is unthinkable for Wenger. He needs to feel the warmth of a domestic victory once more. September could be a month to flip the mood in North London, as Arsenal meet Borussia Dortmund and Olympiakos in the Champions League, Shrewsbury in the Carling Cup and Bolton at home in the league. These are all winnable. In theory.

John Terry's partner: Sideshow Bob's back

Things at the back for Chelsea looked just fine during their opening goalless draw with Stoke, as John Terry and Co. coped relatively well with the Potters' direct approach. But then Terry's defensive partner, Alex, was guilty of having his pants pulled down by Shane Long in the 2-1 win over West Brom. A week later, Andre Villas-Boas played Branislav Ivanovic alongside Terry, but the Serbian failed to reward his manager's faith as he and goalkeeper Hilario combined for a clanger that Grant Holt deftly pounced upon. Holt's goal means Chelsea have only kept one clean sheet in their last seven top-flight matches.

Those two errors that led to goals were not isolated incidents. Indeed, both home matches this campaign have seen Chelsea offer their opponents far too many goalscoring opportunities, which would have been capitalised on by more clinical adversaries. Fortunately for the Blues, though, David Luiz - no stranger to the odd rush of blood, mind - returned to training this week after recovering from a thigh problem. Even more of a boost is shot-stopper Petr Cech making an early comeback from the knee ligament problem he suffered training. This weekend, Chelsea travel to Sunderland, a side who disrupted the West Londoners' backline last term, scoring five goals against them in their two meetings. Let's see how things pan out this time around.

Liverpool: Right back where they started

A chunk of Liverpool's summer transfer discussion was over their need for a new left back. The club duly delivered, landing Jose Enrique from Newcastle. For £5 million, this looks excellent business. Right back, though, looks iffy. England Under-21 international Martin Kelly has undoubted potential, and the same can be said for John Flanagan. But right now, whoever occupies that role appears a weak link in the chain. Of the chances fashioned against Liverpool in their three Premier League matches thus far, often it has been down the opposition's left flank that space has been found and exploited. It was here that Sebastian Larsson popped up to scissor-kick home for Sunderland.

Against Bolton, too, there was cause for concern, in spite of Liverpool cruising. In the 17th minute, Chris Eagles' cross from the right to the back post saw Martin Petrov completely unmarked. Kelly limped off in that match, replaced by Marin Skrtel, who is naturally a centre-half. Reds boss Kenny Dalglish has, though, confirmed this week that Glen Johnson is back in training, the right back absent so far due to a thigh injury. But Johnson is not a reliable defender. His qualities are in the attacking sense, not the positional. Liverpool travel to Stoke this weekend, where their right back will come against deep, diagonal balls and the dribbling ability of Matthew Etherington.

Tottenham: Where's Luka's head at?

Speaking after bottom-of-the-table Tottenham Hotspur's 5-1 hiding by Manchester City, manager Harry Redknapp said: "Luka came to me at 11.30 this morning and said to me, 'I don't feel my head is right today'. I said, 'I feel you need to play today, Luka. I need you to play. You need to come and play'." The transfer window has since closed and Modric remains a Tottenham player, despite reports of a final £40 million bid from Chelsea for his signature. Now Modric simply must get his head down/right/screwed on, whatever metaphor you wish to use, and dedicate himself to Spurs, for it is with them that he signed a six-year contract in 2010. Tottenham need a committed Modric at their disposal.

Penalty takers: It's only from 12 yards

Why have seven of this season's ten Premier League penalties been missed? From 12 yards, the odds favour the taker, not the saver, hence the celebration being more emphatic should the gloved one win this battle of wits. Perhaps goalkeepers are improving? Maybe the game's increased pressures are having an effect? Or, possibly, the striking quality in England's top flight has diminished. Whatever the reason, that is so far a shoddy return from double figures. Blackburn Rovers most recently 'paid the penalty' as they missed two efforts before Everton were 'spot on' (ah, cliched media headlines) to claim all three points. This feebleness followed Brazil shanking four spot-kicks during their penalty shoot-out versus Paraguay in this summer's Copa America. There is a developing trend of penalty wastefulness by professional footballers that is worth monitoring.

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