Watkins was forced off at half-time in England's 3-0 win at Wembley after a heavy collision with the post while attempting to convert a low cross. Although he initially received treatment and attempted to play on, Watkins was substituted before the second half and later described himself as "ok". However, further assessment has seen him return to his club for treatment, ruling him out of the trip to Riga.
The 29-year-old, who scored England's second goal against Wales, has six goals in 20 international appearances but has struggled to find form at club level this season, scoring just once in ten matches. His absence reduces England's attacking options ahead of a potentially decisive qualifying fixture.
A win against Latvia would guarantee England a place at next year's World Cup in the United States, Canada, and Mexico with two games to spare. England currently sit top of Group K, four points clear of second-placed Albania, and are yet to concede in the campaign.
Despite Watkins' injury setback, head coach Thomas Tuchel is expected to welcome back captain Harry Kane, who missed the Wales match due to an ankle issue picked up with Bayern Munich. The 32-year-old has been in prolific form, netting 19 goals in 12 appearances for club and country this season. Kane trained with the squad at Tottenham's training ground on Monday and is expected to lead the line in Riga, fitness permitting.
Should Kane be unavailable, Newcastle's Anthony Gordon could once again be tasked with a central role, having stepped in during the second half against Wales. Marcus Rashford, currently on loan at Barcelona, is another option. Although typically deployed on the left, the Manchester United forward has frequently featured centrally for England and remains the squad's second-highest active scorer with 18 goals.
With Watkins out, Tuchel will travel to Latvia with a 22-man squad as England aim to seal early qualification and maintain their unbeaten run.
England return to domestic action shortly after the international break, with Aston Villa visiting Tottenham on Saturday, October 19.
England manager Thomas Tuchel has confirmed Reece James will miss the World Cup clash with Panama due to a minor hamstring injury but hopes the defender can return later in the tournament.
Manchester City have agreed a deal to sign Nottingham Forest and England midfielder Elliot Anderson for a club record fee of £116m.
New Zealand took firm control of the series-deciding third Test against England after a superb opening day at Trent Bridge, finishing on 361/4 after choosing to bat first.
New Zealand made three changes to their starting XI for the third Test match against England at Trent Bridge on Thursday.
