Armstrong enjoyed an excellent campaign in the Championship for Blackburn during the 2020/21 season, scoring 28 goals in 40 league games.
That was enough to earn him a move to the Premier League with Southampton last summer, although that has not exactly worked out yet.
Can you get 28/28 on this Watford quiz?
The 25-year-old scored just two goals in 28 matches in all competitions during his first season with the Saints, and it seems that could now lead to a summer of speculation around his future.
It is claimed that Southampton are considering loaning Armstrong out this summer, if they can add attacking cover to their side.
However, Armstrong is said to be reluctant to drop out of the Premier League, creating a problem for Watford and ‘Boro, while Southampton do not want to loan him to a top-flight rival.
This would be an excellent signing for Watford if they could manage to get it done.
With Cucho Hernandez and Andre Gray leaving, and Emmanuel Dennis attracting plenty of attention from elsewhere, the Hornets are surely going to have to add to their attacking options this summer.
Armstrong is a proven goalscorer at this level following his prolific spell with Blackburn, so he could be a perfect option to fit that role as well.
Indeed, this would feel like a rather significant statement of intent from Watford if they were to get this one completed, so it does look to be well worth pursuing for those in charge at Vicarage Road.