Arsenal have been dealt a fitness setback ahead of their Champions League clash against Slavia Prague as Viktor Gyokeres missed training following his early withdrawal against Burnley. The £55m striker, who scored in that game before coming off at half-time, was nowhere to be seen as Mikel Arteta’s side prepared for Tuesday’s trip to the Fortuna Arena.Arsenal’s preparations for their Champions League encounter with Slavia Praha suffered a blow as Gyokeres missed Monday’s training session at London Colney, as per Charles Watts. The Swedish striker, who opened the scoring for the Gunners with a composed finish in the 2-0 win at Burnley, was taken off at half-time after feeling discomfort in his leg. Arteta later confirmed that the forward had picked up a 'muscular niggle' and would undergo further assessment to determine the extent of the issue.Speaking after the Burnley win, Arteta praised Gyokeres’ performance, saying: “I think that was one of the best games he has played. His performance was exceptional – his high press, his running in behind, the way he linked play, everything. It’s a shame that he felt something. We had to take him off because of a niggle, so we’ll have to wait and see.” With Gyokeres absent from training and Gabriel Martinelli, Kai Havertz, and Gabriel Jesus also sidelined, Arsenal’s attacking options are suddenly looking thin.The absence of Gyokeres leaves Arteta facing a potential selection dilemma for the trip to Prague. Makeshift forward Mikel Merino, who replaced the Swede at Turf Moor, may again be asked to lead the line, while teenage striker Andre Harriman-Annous could be drafted into the squad. Kepa Arrizabalaga also missed training for undisclosed reasons, though Martin Zubimendi did participate but is suspended for the match after picking up three bookings in the group stage already.Gyokeres’ potential injury comes at an unwelcome time for Arsenal, who are in blistering form across all competitions. Saturday’s victory at Burnley marked their ninth consecutive win and extended their lead at the top of the Premier League table to six points. Their defensive record has been impeccable, while in attack, Gyokeres had begun to find rhythm after a somewhat cautious start to life in England.The 25-year-old’s integration into Arteta’s system has been one of Arsenal’s key storylines this season. Signed from Sporting CP for an initial £55 million in July, Gyokeres arrived with enormous expectations after scoring 97 goals in 102 appearances in Portugal. His physical presence and work rate have quickly made him a valuable addition to Arsenal’s attack, offering a more traditional focal point compared to the frontlines of previous seasons.Before his setback, Gyokeres had enjoyed a steady adaptation to the demands of the Premier League and Champions League. Across 14 appearances in all competitions this season, he has scored six goals and logged over 1,000 minutes. His contribution has not only come in scoring but also in his ability to stretch defences, creating space for Arsenal’s midfielders to operate effectively.Gyokeres ranks among the league’s most active strikers in terms of touches inside the penalty area, with 38 offensive actions in the box so far this season. His pressing and off-ball movement have drawn praise from Arteta, who believes the Swede’s intelligence in positioning has been key to Arsenal’s improved attacking patterns. “He gets us from defensive situations into transitions very quickly,” Arteta noted recently. “He gives us presence and aggression that changes how teams defend against us.”Arsenal’s medical staff will now assess Gyokeres’ condition ahead of a demanding stretch of fixtures. With Martinelli, Havertz, and Jesus all sidelined, the Gunners’ depth in attack is being tested. The timing is particularly difficult, with a trip to Sunderland in the Premier League coming just four days after the Champions League fixture, followed by a high-stakes north London derby against Tottenham after the international break.Arsenal will travel to Prague without Gyokeres, barring a late surprise, and Arteta will likely be forced into tactical reshuffling for the midweek fixture. Arsenal will be favourites to maintain their perfect Champions League record this season.Post-match, all eyes will be on Arteta’s fitness update regarding Gyokeres, with fans anxious about his availability for domestic fixtures. A short-term absence would be manageable given Arsenal’s current momentum, but a longer spell on the sidelines could affect their fluency in attack.