Mikel Arteta has been handed an early selection headache as Arsenal prepare for a highly anticipated London derby against Chelsea at the Emirates Stadium, with Bruno Guimaraes and Cristhian Mosquera both absent from Thursday’s open training session.

The Gunners have made a perfect start to the 2026/27 Premier League campaign, winning their opening two matches against Coventry City and Aston Villa, but their preparations for the visit of Chelsea have been clouded by concerns over the fitness of two summer arrivals. While neither absence has been officially confirmed as a serious injury, their failure to appear during the session has naturally raised questions about their availability for Sunday’s meeting.

Arsenal will be particularly keen to avoid adding further names to their Arsenal’s injury list at such an early stage of the season, especially with Chelsea also arriving at the Emirates in impressive form after recording victories in both of their opening fixtures.

Arsenal Injury Concerns Ahead of Chelsea

Arsenal’s preparations for their first major domestic test of the new season have been complicated by the absence of Guimaraes and Mosquera from Thursday’s training session at London Colney, although the circumstances surrounding the two players are understood to be different.

The most immediate concern surrounds Guimaraes, who arrived from Newcastle United during the summer transfer window in a high-profile £75 million deal designed to strengthen Arsenal’s midfield. The Brazil international missed the Premier League opener against Coventry City because of a persistent groin problem, before returning to action during Monday’s 1-0 victory over Aston Villa.

However, Guimaraes was only introduced from the bench for the final 19 minutes at Villa Park, suggesting that Arsenal’s medical and coaching staff are still managing his workload carefully. His absence from Thursday’s session therefore provides another reason for caution, particularly with Arteta facing a Chelsea side capable of testing Arsenal’s midfield physically and technically.

The midfielder’s presence could prove particularly valuable because of his ability to provide defensive protection while also helping Arsenal progress the ball from deeper areas. Although the Gunners have considerable strength in midfield, losing a £75 million summer signing for a fixture of this magnitude would represent an unwanted complication for Arteta.

Cristhian Mosquera absent from training

Mosquera’s situation appears slightly different, as the defender was taken off during Arsenal’s victory over Aston Villa after appearing to feel discomfort late in the match.

The 22-year-old was replaced by Ezri Konsa in the 79th minute, but Arteta offered a relatively reassuring assessment immediately after the game, explaining that the decision was precautionary because Mosquera felt as though he was “about to have something”.

Despite that positive initial assessment, Mosquera’s absence from Thursday’s training session means Arsenal will have to monitor his condition closely before making a final decision on his involvement against Chelsea.

Arsenal’s Injury List Could Test Arteta’s Depth

If Mosquera is unable to recover in time, Konsa appears to be the obvious option to step into the defense after replacing him at Villa Park. The former Aston Villa defender completed a £51 million move to Arsenal during the summer and could now be handed his first full home appearance for his new club against his former employers.

That possibility adds an intriguing subplot to an already important fixture, but Arteta will be more concerned with maintaining the defensive stability that has helped his side begin the campaign with two consecutive clean sheets.

The situation is made more complicated by the fact that Jurrien Timber is also considered a doubt for the weekend, meaning Arsenal’s injury list could force Arteta to make adjustments sooner than he would have wanted. The manager will therefore hope the latest absences are largely precautionary rather than signs of injuries that could keep either player out for an extended period.

For Guimaraes in particular, Arsenal are likely to continue taking a cautious approach given his existing groin problem. The club invested heavily in the midfielder because of his importance to Arteta’s plans, and rushing him back for one fixture could create a greater problem further down the line.

Arsenal and Chelsea Set for Early London Derby

The stakes surrounding Sunday’s London derby are already unusually high despite the season being only two matches old. Arsenal and Chelsea have both collected maximum points from their opening fixtures, meaning the meeting at the Emirates provides an early opportunity for one side to establish an advantage over a direct rival.

Arsenal began their 2026/27 Premier League campaign with a convincing 3-0 victory over Coventry before securing a narrow 1-0 triumph away to Aston Villa, demonstrating both attacking quality and defensive resilience. Chelsea, meanwhile, have produced more open contests, beating Fulham 3-2 before edging past Brighton 4-3 in another high-scoring encounter.

The contrasting nature of those victories could make Sunday’s contest particularly fascinating, with Arteta’s Arsenal likely to value control and defensive structure against a Chelsea team that has already demonstrated its capacity to create and convert chances.

For Arteta, however, the immediate priority will be determining the fitness of Guimaraes and Mosquera before the weekend. Their presence would give Arsenal greater depth and tactical flexibility, while their absence could force the manager to rely on the strength of his squad earlier than planned.

As the London derby approaches, Arsenal will hope Thursday’s training absences prove to be nothing more than sensible precautions. With both teams unbeaten and perfect after two games, the Emirates is set to host one of the first major statements of the new Premier League season.