Diamanti has been training with Watford for more than a week but his move, understood to be a season-long loan, from Chinese side Guangzhou Evergrande is yet to be officially confirmed.
Watford host West Brom, hoping to build on an encouraging 2-2 draw at Everton in the Barclays Premier League last weekend, and Diamanti could make his debut if the transfer goes through before midday on Friday.
"Will the move be completed in time for Saturday? It is difficult for Saturday but it's close," Flores said.
"He's training with us every day, he's performing well - the teams are talking to arrange the last details and he has the possibility to be incorporated onto the list."
Diamanti scored eight goals for West Ham in 2009-10 and is set to become Watford's 11th signing of the summer.
"Now we have a good group of players who can play differently, who can make the ball move quickly in the last third," Flores said.
"We need speed
We now have (Steven) Berghuis, (Almen) Abdi, (Jose Manuel) Jurado, Diamanti - this is part of the style of the team.
"If you allow the players to attack, they will attack with freedom and that is good for us.
"He brings technical qualities, vision of the pitch and he is really strong at set-pieces with free-kicks so it is very, very nice to have him
He also has experience, which is important for us."
Watford led twice against Everton but a late Arouna Kone goal denied the Hornets victory on the opening day of the season.
Flores handed six players their debuts at Goodison Park and the Hornets' head coach believes the best is yet to come from his much-changed squad.
"It's only the first match
We are really, really far away from the sort of performance we could produce at the end of the season," Flores said.
"We have only worked for six weeks together and we are incorporating new players every week
We are still a long way from the performance we could produce."
Flores added: "It's a necessity to remove the idea that we are new and with innocence to be competitive in this league.
"We want to improve but it's very important we show to the league we are an experienced team who can manage different situations."
West Brom's start to the season was less assured as the Baggies were thrashed 3-0 at home by Manchester City.
Tony Pulis' side were uncharacteristically sloppy in defence and Flores is urging his players to dominate the contest at Vicarage Road.
"We don't need to change the mentality, the opposite, we have to enforce the things we did against Everton," Flores said.
"But the match will be completely different - we are playing at home, West Brom are maybe not interested to keep the ball, always playing long ball.
"For us, our aim is to control the ball, to try to defend high - sometimes it was impossible to do against Everton because Everton are a good team with a lot of experience and players who can play very quick.
"Against West Brom I think it will be a little bit different."
Abdi and Berghuis are both available again for Watford after the duo recovered from knee and upper leg injuries respectively.
Source : PA
Source: PA