The Spanish midfielder has struggled with a string of injury problems to hand McTominay the chance to shine in the Manchester United team.
The newly-capped Scotland international has earned the trust of Jose Mourinho thanks to his composed performances in the middle of the park.
McTominay has featured in nine Premier League games and helped Manchester United to secure a 2-1 win against Chelsea FC at Old Trafford last month.
The versatile midfielder started Manchester United’s goalless draw with Sevilla in the first leg of their Champions League last-16 clash to highlight his growing importance.
Manchester United are set to lose Carrick to retirement at the end of the 2017-18 season, while Marouane Fellaini’s current deal will expire in the summer.
Herrera is confident McTominay can establish himself as a regular in the Manchester United team.
“You saw against Chelsea he was a little more defensive and almost doing the job I did against [Eden] Hazard last season, not exactly the same but similar. He can be more offensive as well and he presses a lot,” Herrera told Man United’s website.
“We know we’re not going to have Michael Carrick after this season so we need to add more midfielders to the team and I think Scott is really ready to play in the Premier League and help the team.”
Manchester United finished in sixth place in the Premier League table last term but won the EFL Cup and the Europa League in Jose Mourinho’s first season in charge.
The Red Devils signed Chile international Alexis Sanchez in the January transfer window.
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