The winger has signed on the back of two hugely productive seasons for German side Bayer Leverkusen.
He scored 22 goals and supplied 20 assists across 65 league appearances in that period.
Villa head coach Unai Emery has suggested the France international's versatility can help shape his tactics.
"Moussa Diaby is a player that we were following and he is helping us try to improve our level playing in the attacking third," he said.
"Sometimes he plays right, sometimes he plays as a No 10, sometimes as a left winger."
That all-round ability, combined with his relatively low cost of £6.5m, suggests Diaby could be a big success in Fantasy this season.
His new team-mate Watkins was transformed after Emery took charge in Gameweek 15 last season.
Indeed, Watkins was the third-top-scoring forward in Fantasy during that period, averaging 5.6 points per match thanks to 13 goals and six assists.
But it is Emiliano Buendia (£6.0m) who has been Villa's standout player, scoring twice and assisting Watkins’ goal in that 3-3 draw with Newcastle earlier this week.
Villa face the Magpies again in Gameweek 1 of 2023/24 Fantasy, and their subsequent early schedule certainly looks encouraging for their attacking players.
Following their meeting with Newcastle, three of Villa's subsequent four matches score only two in the Fixture Difficulty Ratings (FDR).
Villa's GW 1-5 schedule
While Watkins currently offers the most reliable route to Villa's attack, Diaby’s low cost and all-round potential can help him challenge the forward as their best pick in 2023/24.
Also in this series
Part 1: Flekken can be Brentford’s No 1
Part 2: Advanced role will lift Mac Allister’s appeal
Part 3: Midfield role could lift Nkunku's appeal
Part 4: Kluivert can continue rapid improvement
Part 5: How new role can help Havertz thrive
Part 6: How Maddison compares with Spurs' attackers
Part 7: Can Mount rival Rashford and Fernandes?
Part 8: Onana can be top-scoring goalkeeper