Wright comes into central midfield after Mattsson was ruled out for ‘several’ weeks with the ankle problem that forced him off at half-time against Coventry.
The Belgian confirmed on Friday Mattsson does not require surgery, but indicated City must now weigh up whether to make a late-transfer window move ahead of Monday’s deadline, with fellow central midfielder Mirko Topic already out for the season with an ACL knee injury.
Diallo replaces Tony Springett in the line up from the 2-1 home win over leaders Coventry City. But recent Manchester United loanee Harry Amass is not in the matchday squad. Clement did hint at his pre-match media call there were other fitness concerns in the camp.
New signing Paris Maghoma was not in contention for Boro, with the recent arrival from Brentford still overcoming a six-month lay-off with two hamstring-related injuries.
Shane Duffy (hamstring), Jeffrey Schlupp (hamstring), Topic and Ante Crnac (ACL knee injuries) and Gabe Forsyth (knee) are longer term absentees.
Lucien Mahovo is expected to miss the majority of the run in with a muscular problem.
Clement confirmed at Colney on Friday Amankwah Forson was due to return to team training next week after his hamstring lay-off dating back to the December trip to Preston.
Watch live reaction from our reporters at Carrow Road to the team news
Middlesbrough (starting XI): Brynn, Brittain, Targett, Hackney (C), McGree, Conway, Whittaker, Ayling, Browne, Morris, Malanda. (Subs): McLaughlin (GK), Fry, Strelec, Gilbert, Munroe, Nypan, Silvera, Hansen, Sarmiento.
Norwich City (starting XI): Kovacevic; Fisher, McConville, Cordoba, Chrisene; McLean (C), Wright; Diallo, Slimane, Ahmed; Makama. (Subs): Grimshaw (GK), Stacey, Darling, Gibbs, Jurasek, Marcondes, Schwartau, Kvistgaarden, Mundle-Smith.
Referee: Ben Toner