Mikel Arteta: 8
He fitted in Arsenal's playing style seamlessly as if he had been playing in the red and white for years. In Arsenal's so far struggling season, he seems to be one of a few consistent performers (the most consistent player is Sagna, who is unfortunately sidelined for at least three months). He is thought to have been brought in to replace Fabregas, but due to Jack Wilshere's long-term injury, he is playing a deeper role, while Ramsey is taking more attacking responsibilities.
I personally did not see Arteta as Fabregas' replacement. Ramsey has always been an intended successor of Fabregas and in my view, Ramsey-Wilshere-Song(/Frimpong/Coquelin) should be Arsenal's future midfield. Arteta is there to help the young players' progress. So I am quite happy with his performances so far. He brought much-needed stability to Arsenal midfield. He may not have Fabregas' creative flair but he is a lot better defender than Fabregas and more accomplished all-round midfielder.
Per Mertesacker: 6
Story so far: Like Arteta, Mertesacker also played all games except for the Carling Cup tie since he joined Arsenal.
It is not fair to assess his performances in the current chaotic situation surrounding Arsenal's back-four nor to expect him to solve Arsenal's defensive problems instantly. He was signed during Vermaelen's absence, had to form a central defensive partnership with Koscielny immediately, and when it seemed starting to establish, Koscielny got injured. Then he had to pair with the makeshift centre-back, Song, as no recognised centre-backs were available due to the injuries.
Some have already concluded that the purchase of Mertesacker was a "miss" based on the fact that Arsenal have conceded 8 goals (exclusive of the one in the Carling Cup match) since Mertesacker joined them. Gary Cahill's Bolton and Chris Samba's Blackburn have conceded 16 and 13 goals, respectively, in the EPL this season (I haven't checked how many of these goals are actually from the games these defenders played in, though), while Bolton have kept just one clean sheet and Blackburn none, as opposed to Arsenal's three (two with Per). My points are that you cannot judge defenders' performances from their teams' defensive records and that even if Arsenal had signed defenders with a wealth of Premier League experience, such as Cahill or Samba, they might still have been unable to eradicate Arsenal's defensive frailty.
Per's performance has been gradually becoming solid. Once Vermaelen is back from the injury and start establishing a steady partnership with him, he will show his real class as an experienced German international.
Andre Santos: 7
Story so far: Santos made his debut against Blackburn on 17 September. He also played 90 minutes against Olympiacos, helping Arsenal to register their first win in the CL group stage through his first goal for his new club.
Although he only played two games, which may not be enough to evaluate his performance, he looks a decent player, certainly good enough to share the starting place with Gibbs, who cannot be risked in too many games (Gibbs is still the first-choice left-back). My only worry is his defensive reputation, which is not up to scratch. That said, I must say I haven't seen particularly bad defending from him yet. Overall, he is a valuable addition to the squad especially because Traore was not up to Arsenal's standard (no disrespect to QPR).
Yossi Benayoun: 6
Story so far: Benayoun made his first appearance for Arsenal from the bench against Swansea, followed by full 90-minute appearances against Dortmund and Shrewsbury Town. He missed two games through a thigh strain, but was fit enough to come off the bench at the 72nd minute for Theo Walcott against Tottenham.
He was instrumental to the win over Shrewsbury Town, even scoring his first goal in an Arsenal shirt. He did not make an impact when he came on the pitch against Tottenham. Without doubt he is a good addition to the squad. Hopefully he will make a difference to Arsenal's games in the future.
Story so far: Gervinho made his debut in the opening game against Newcastle, which was cut short due to the red card. As a consequence, he missed the following three Premier League matches, while he took part in Arsenal's CL play-off victories over Udinese and draw with Dortmund during the domestic suspension. In his first game back from suspension against Blackburn, he scored his first goal of the season. He started in the following Premier League match against Bolton and played till the 76th minute when he was substituted by Andrey Arshavin. Although he missed the Olympiacos game through an injury, he passed fitness tests and played 77 minutes against Tottenham till he was replaced by Arshavin.
He seems to have already secured the starting place on the left wing ahead of Arshavin, Benayoun, and Ryo, but I don't think he has fulfilled his abilities yet. He made a very impressive debut in his cameo appearance in the pre-season match against Cologne. He is a skillful player good enough to fill Nasri's boots as a winger. On top of it, his direct style of play is something Arsenal have been missing for years. Yes, he should have passed the ball to RVP in the Blackburn game, which would have resulted in a third goal that should have killed off the game, but didn't we all want a "selfish striker"? He is a breath of fresh air among those typical Arsenal players who are reluctant to shoot.
At the moment, I am a little bit disappointed with him probably because my expectations were too high after his breath-taking debut in the pre-season, but I am sure there will be still more to come from him. It seems to me that he is still in search for the right balance of expressing himself and fitting into Arsenal's style of play. It naturally takes some time to adapt as his style is different from that of his new club.
Alex Oxlade-Chamberlain: 8
Story so far: Chamberlain made his debut from the bench in the defeat to Manchester United. Although his starting debut had to wait until the Carling Cup tie against Shrewsbury, it was worth waiting as he scored his first goal for Arsenal and displayed the man of the match performance. He left the pitch in a standing ovation to make way for Chuks Aneke at the 90th minute. Following the success, he had another chance to show his quality in the hard-fought win over Olympiacos. He played 68 minutes, during which he scored his second goal of the season and engraved his name in the history as the youngest English player to score in the Champions League. His sparking form has been continuing during the international break with his hat-trick against U-21 Iceland.
By now we have all seen why he came with the rather hefty price tag for an 18 year-old. His performances against Shrewsbury Town and Olympiacos were sensational. With his pace, trickery, strength, flair, and composure, he will be a strong contender for a regular starting place on the right wing soon and his rise could open out various possibilities, including Walcott's dream move to the central striker role. AOC presents exciting prospects and massive potential for Arsenal. But first, we want to see more of him in the near future.
Carl Jenkinson: 5
Story so far: Jenkinson made his first appearance this season in the CL play-off against Udinese at the Emirates as a 55th-minute substitution in the unfamiliar left-back position . In the following game against Liverpool, he made his full debut at right back as Sagna filled in the left-back due to the injuries to Gibbs and Traore. He played 90 minutes in Arsenal's second-leg win over Udinese. He started at right back against Manchester United due to Sagna's illness, but he was omitted from the squad for the following three games. His next appearance was in the 3-1 win over Shrewsbury Town with other second-string players of the first team squad. After spending 90 minutes on the bench against Olympiacos, he came on the pitch against Tottenham at the 68th minute to replace Sagna, who had a fractured fibula on his right leg.
His performance has been mixed so far, including his torrid time at Old Trafford. He has enthusiasm and good crossing, but his reading of the game and positioning leave much to be desired. Whether you like him or hate him, it is a fact that he has to play every game from now on for at least three months during Bacary Sagna's absence, unless Arsene Wenger has other options. I wish Eboue had stayed with us. Although he was error-prone, at least he was tested and proven. Let's hope the ex-Charlton player will improve immensely as he plays more games.
Ju Young Park: N/A
Story so far: Park was an unused substitute in the matches against Swansea, Dortmund, but he finally made his debut against Shrewsbury in the Carling Cup third-round tie. He was once again on the bench against Olympiacos and Tottenham, but did not make appearances. His form for South Korean national team has been impressive, including a hat-trick during the September international break and two goals in the draw against Poland last Friday.
He did OK against Shrewsbury Town, with some nice moves, but not enough to make a difference. He is likely to continue sharing a place on the bench with Chamakh and may have chances to feature in the domestic Cup competitions. Apparently he played the lone striker role at Monaco. Many Asian fans are eagerly awaiting his first-team action, but at the moment, it is difficult to see Wenger choose him in front of RVP.
Story so far: His first-team action has been limited due to his calf injury and stiff competition for the left-wing position. After spending 90 minutes on the bench against Liverpool, he finally made his first-team dubut of the season at the 72nd minute against Shrewsbury to replace Ju Young Park. In between these games and thereafter, he started in three reserve games.
Again, we haven't seen him play enough games to rate his performance. Following the successful start to his professional career at Feyenoord, many fans are desperate to see him play more games for Arsenal, but I'd rather he would be given time to develop. At the moment, reserve games seem to be the best option for him. He has not made a big impression in reserve games yet. Hopefully, we will see him again in the next Carling Cup game.