The Ghanaian midfielder has missed Arsenal’s previous three Premier League matches with a thigh issue.
Partey was reportedly eyeing up a return at the weekend against Everton before the match was postponed.
However, Watts believes that the extra week to prepare means Partey will be fit for Arsenal’s London derby against Brentford.

Mikel Arteta’s side were desperate to bring in another central midfielder on deadline day.
Arsenal made a bid for Aston Villa’s Douglas Luiz, but Steven Gerrard’s side rebuffed their offers.
Thomas Partey has suffered several injury setbacks in his time at The Emirates.
Arsenal wanting another man to potential fill that role is no surprise, although Partey’s performances make it difficult to drop him when fit.
Partey will be fit to face Brentford
Watts said: “Good news is as far as I’m aware Thomas Partey is going to be available for this game against Brentford.
“Mikel Arteta is going to have to make a decision on it at the end of this week.
“From what I understand, Thomas Partey returned to full training towards the end of last week.
“He felt like he would have been available to play against Everton had it been on.
“He’s had an extra week of training now and I can’t see why he wouldn’t be involved.
“If everything goes to plan and he stays fit and he’s had another week’s training, I don’t see why he wouldn’t be involved against Brentford.”

The £45m signing from Atletico Madrid joined two seasons ago, but has suffered six separate injuries in that time.
Arteta will be desperate for the 29-year-old to stay fit until the next transfer window.
The games will be coming thick and fast for Arsenal, and his minutes may need to be managed.
This could give Albert Sambi Lokonga more opportunities in midfield, who is likely to miss out as Partey returns.
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