The Hornets have secured an instant return to the Premier League as runners-up in the second tier and the Welsh side will be hoping to join them.
After securing their promotion with victory over Millwall a fortnight ago, Watford may blame the celebrations for their 2-0 defeat to Brentford last weekend.
It was only their second loss since the beginning of March – a period which has seen them pick up 28 out of a possible 36 points and surge into the top two.
The Hornets have the best home record in the Championship this season, picking up 56 of their 88 points at Vicarage Road. No other team has more wins (18), suffered fewer defeats (two), scored more goals (42) or conceded fewer goals (12) on home turf.
Incredibly, Xisco Munoz's side have won their last eight consecutive matches in Hertfordshire and kept clean sheets in seven of them.
Swansea have been automatic promotion contenders themselves for much of the season; indeed their 2-1 win over Watford at the start of January – courtesy of a Jamal Lowe brace – took them into the top two.
However, they have dropped off in the second half of the campaign and must now settle for a spot in the playoffs for the second consecutive season.
Two goals in the space of three minutes from Morgan Whittaker and Connor Roberts helped Steve Cooper's side come from behind to beat Derby County 2-1 last weekend but that was only their third win in 10 games.
It did move them up to fourth in the table, a position they will want to keep to secure home advantage in the playoff semi-final second leg; they would drop to fifth if they lose at Vicarage Road and Bournemouth beat Stoke City.
The Cherries or Barnsley will be Swansea's opponents in the end-of-season lottery, with Cooper admitting "whoever we play, they are going to be difficult ties".
The Swans have the third-best defensive record in the Championship this season, while only Norwich City and Brentford have picked up more points away from home.
In midfield, Tom Cleverley suffered a hamstring problem against Brentford to join Nathaniel Chalobah on the treatment table, while Ismaila Sarr is unlikely to feature with the club stating "no risks will be taken" with the electric winger.
However, club captain Troy Deeney hopes to play some part for the first time since suffering an Achilles injury in February and Joao Pedro is also expected to be back available after missing the Brentford defeat.
Andre Ayew missed Swansea's win over Derby but is expected to feature on Saturday, perhaps as a substitute, with Cooper admitting "he will need some minutes" ahead of the playoffs.
Watford possible starting lineup:
Bachmann; Cathcart, Sierralta, Troost-Ekong, Masina; Hughes, Gosling, Zinckernagel; Success, Pedro, Sema
Swansea City possible starting lineup:
Woodman; Roberts, Guehi, Cabango, Bidwell; Grimes, Fulton, Hourihane; Whittaker, Cullen, Lowe
We say: Watford 1-1 Swansea City
This game looked like it might be a promotion-decider a few weeks ago, but with Watford over the line and Swansea now focused on the playoffs, both teams might play it fairly safe – particularly with the Hornets depleted through injuries and the Swans monitoring several players. We think that it will end all square.