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McNicholl has been included as one of five uncapped players in Wayne Pivac's first 38-man Six Nations squad.
McNicholl's selection is not a surprise after he scored a try in his non-capped debut against the Barbarians late November but he is now set to line up alongside fellow Kiwi Hadleigh Parkes.
McNicholl, who has satisfied the residency rule after three years with Scarlets, would've been joined by former Hurricanes midfielder Willis Halaholo and Gareth Anscombe but for their injuries.
Since his Pro14 debut in 2016, no other player has scored more tries (26) or made more breaks (69) than the 29-year-old McNicholl.
Pivac made a splash with his first Six Nations squad since succeeding Warren Gatland by calling up 18-year-old Louis Rees-Zammit, the Gloucester wing who was courted by Eddie Jones after scoring nine tries in 10 games for his English club this season.
Saracens centre Nick Tompkins, born and raised in England and having represented their under 20 side, Sale prop WillGriff John and Wasps lock Will Rowlands are the other uncapped call ups for the defending Six Nations champions.
Other features of the squad include the return of British and Irish Lions No 8 Taulupe Faletau who missed the World Cup due to a broken collarbone and last played for Wales two years ago.
Halfback Rhys Webb is another to end a two-year test exile, having been ineligible for Wales since the 60 cap threshold for those playing outside the country was introduced.
The Welsh Rugby Union confirmed earlier this month Webb will be eligible for immediate selection after announcing he will return from Toulon to rejoin Ospreys next season.
Tompkins, 24, represented the England Saxons in 2016 and is an England under 20 World Cup winner, but he qualifies for Wales through his Wrexham-born grandmother.
Despite Tompkins playing for the Saxons, he was not captured by England because their opposition, South Africa A, were not South Africa's officially-recognised second team at that time.
Tompkins gives Pivac additional midfield cover, with Scarlets centre Jonathan Davies sidelined for the entire Six Nations and Ospreys' Owen Watkin recovering from a knee problem.
"We are really excited to be naming our Six Nations squad and kicking the campaign off," Pivac said.
"A lot of time and effort has gone into selecting the squad, all of the coaches have been out and about, seeing players in training, speaking with them and we are pretty excited with the group we have got.
"Looking back to the Barbarians week, that was hugely important for us. We got a lot of 'firsts' out of the way, getting to meet and get in front of the players and having a game together was hugely beneficial.
"We do have a couple of injuries but we flip that into seeing it as an opportunity for some new players to impress, with not only the Six Nations in mind but also longer term and 2023.
"The Six Nations is hugely exciting for me, it is something I grew up watching from afar and it has such history attached to it, I'm really looking forward to the campaign."
Wales open their Six Nations campaign against Italy in Cardiff before travelling to Dublin the following weekend.
Wales Six Nations squad:
Forwards: Rhys Carre, Rob Evans, Wyn Jones, Elliot Dee, Ryan Elias, Ken Owens, Leon Brown, WillGriff John, Dillon Lewis, Jake Ball, Adam Beard, Seb Davies, Alun Wyn Jones (c), Will Rowlands, Cory Hill, Aaron Shingler, Aaron Wainwright, Taulupe Faletau, Ross Moriarty, Josh Navidi, Justin Tipuric
Backs: Gareth Davies, Rhys Webb, Tomos Williams, Dan Biggar, Owen Williams, Jarrod Evans, Hadleigh Parkes, Nick Tompkins, Owen Watkin, George North, Josh Adams, Owen Lane, Johnny McNicholl, Louis Rees-Zammit, Jonah Holmes, Leigh Halfpenny, Liam Williams