Jermain Defoe has hailed Lee Cattermole's mental strength and positive influence on the Sunderland dressing room.
The 29-year-old recently returned to the Sunderland side after six-months out with a hip injury, with the midfield enforcer a big miss during his time on the treatment table.
Cattermole has been at Sunderland since the summer of 2009 but came through the Middlesbrough academy as a youngster.
Sunderland face relegation rivals Boro at the Riverside Stadium on Wednesday night and Defoe has hailed the influence of Cattermole ahead of the bottom-of-the-table clash.
"We have missed him and we have been unlucky with injuries this season," said Defoe.
"With Catts, he is a key figure in the dressing room and has been here for years and understands.
"In our position we have missed him - especially in that position - and it has been hard for us along with the other injuries - Dunc, Jan and the others.
"To have him back is really good. I just feel that he has done really well since he got back.
"To come back and get that level of fitness as the other boys is difficult but he is that type of character. He is mentally strong and gives everything - especially in training.
"Because he does that it feels good to have him back and to have him back is really important for the team," added the 34-year-old to the club website.