Calum MacRae has named three debutants in his side ahead of the HSBC World Rugby Sevens Series in Hong Kong this weekend.Glasgow Warriors’ Grayson Hart, Edinburgh Rugby’s Blair Kinghorn and Scotland U20 back Darcy Graham will all feature on the Sevens circuit for the first time.Scrum-half Hart, who has three Scotland caps, has played 32 times for the Warriors following a stint with Edinburgh Rugby and has Super Rugby experience playing in New Zealand and Australia.Kinghorn (20) has already played 35 times for his club and his sevens debut follows being capped for Scotland at U18 and U20 levels.BT Sport Scottish Rugby Academy prospect Graham has been in fine form this season, playing every game for Scotland at the U20 6 Nations.Earlier this year it was announced that his eye-catching performances had earned him a professional contract with Edinburgh Rugby ahead of the 2017/18 season.Harlequins winger Robbie Nairn also joins the squad.Scotland 7s Head Coach Calum MacRae said: “Having lost Scott Riddell to injury, it’s great to have Hugh Blake co-captaining the squad with Scott Wight.”It is a chance for Hugh to show how much he has developed as a person and a leader.”We have three new caps in Darcy Graham, Grayson Hart and Blair Kinghorn, all of whom understand the work ethic that is expected and required.”This is a great opportunity as part of their development to put a marker down and show what they are about.With Robbie Nairn and Ally Miller making selection it’s a younger but very able group.”Heading into the back half of the series it’s been important that we maintain focus on improving aspects of our own performance.”Hong Kong is the tournament everyone raises their game for and it’s a great challenge starting this Friday.” Scotland 7s fixtures in the seventh leg of the World Rugby HSBC Sevens Series in Hong Kong, Friday 7 – Sunday 9 April (kick-off times in GMT)7 April11.44am – Argentina 7s v Scotland 7s8 April5.26am – USA 7s v Scotland 7s9.02am – Scotland 7s v Russia 7s TBC  Scotland 7s squad to compete in Hong Kong (World Series tournaments in brackets) 1.     GRAYSON HART (0)2.     DOUGIE FIFE (12)3.     ALLY MILLER (2)4.     DARCY GRAHAM (0)5.     BLAIR KINGHORN (0)6.     MARK ROBERTSON (53)7.     JAMIE FARNDALE (17)8.     JO NAYACAVOU (23)9.     HUGH BLAKE (12) CO-CAPTAIN10.  SCOTT WIGHT (26) CO-CAPTAIN11.  JAMES FLEMING (39)12.  ROBERT BEATTIE (3)13. ROBBIE NAIRN (2)