Renato Sanches, Sam Clucas and Tammy Abraham return in place of Leroy Fer, Wayne Routledge and Oliver McBurnie.
While Swansea have today announced that Carvalhal has named fellow countrymen Joao Mario and Bruno Lage on his coaching staff, as former player-assistant coach Leon Britton returns to the playing staff.
Britton did explain: “In fairness to the manager and chairman, they offered me the opportunity to stay as part of the new coaching set-up.”
The new Swans manager has opted for a diamond system against the Hornets. Carvalhal often used 4-4-2 during his time at Sheffield Wednesday however he did write a book that more than included the positives of the 4-3-3 system.
However it does look like he will use the diamond shape that several Swansea managers have tried before.
Clucas, Tom Carroll and Roque Mesa are expected to make up the base of the diamond, while Sanches should operate at the tip.
Handing Sanches a start after a turbulent first half of the season for the midfielder is a bold call by Carvalhal, but he certainly does have the quality to shine.
Speaking on Sanches, Carvalhal previously said: "I think he [Sanches] needs confidence,
"It is easy to forget because he has played for Benfica and the Portuguese national team that he is still only a kid.
"He is still learning and I think he needs a role in the team.
The manager said in his pre-match press conference: "With time he will understand all the different roles the players have in the team.
"But he will be involved in the dynamic and, when he understands what we want, he will be a completely different player." The 52-year-old said. "We believe that."
The Hornets used a 4-3-3 shape during their 2-1 win over Leicester City.
A similar system looks like it will be in place to face Swansea, but Richarlison will return to the wing and Okaka gets the nod over Andre Gray up front.
Wilfried Bony misses out once again with a hamstring injury, while Kyle Bartley and Ki Sung-Yueng remain out but are on the comeback from injuries.
Bony has missed the last two games with a hamstring injury, this third of the king this season after returning to first-team football for the first time since his initial run of games at Manchester City.
Watford: Gomes, Janmaat, Wague, Kabasele, Zeegelaar; Watson, Doucoure; Carrillo, Cleverley, Richarlison; Okaka.
Swansea: Fabianski; Naughton, Fernandez, Mawson, Olsson; Clucas, Mesa, Carroll, Sanches; Ayew, Abraham.