Lacazette first felt the ankle problem during Arsenals pre-season friendly with Lyon and subsequently missed the sides Premier League opener against Newcastle.
The Frenchman returned to Unai Emerys starting XI for a 2-1 win over Burnley before making a substitute appearance in Arsenals 3-1 defeat at Liverpool the following weekend.
After starting and scoring in Arsenals 2-2 draw with Tottenham, it was assumed Lacazette had fully recovered from his ankle injury but the striker is set to be sidelined for the remainder of September.
After assessments to an ongoing ankle issue, we have advised that Alex will need to rest and strengthen his ankle to regain full fitness, an Arsenal statement said on Friday ahead of the sides trip to Watford.
Alex has been playing through this injury for several weeks.
He is likely to be back in action in October.
Matches Lacazette will likely miss
Watford vs Arsenal – Premier League (Sept 15)
Franfurt vs Arsenal – Europa League (Sept 19)
Arsenal vs Aston Villa – Premier League (Sept 22)
Arsenal vs Nottingham Forest – EFL Cup (Sept 24)
Manchester United vs Arsenal – Premier League (Sept 30)
Emery confirmed that Kieran Tierney and Hector Bellerin will miss Arsenals trip to Vicarage Road despite both full-backs returning to training this week.
Asked whether they could return, Emery replied: Not yet. It depends on their progress for the next weeks.
Maybe we can decide to play at the beginning with the U23s, to be ready with us.
Maybe if they play with the U23s they can take confidence and then after play with us 100 per cent.