Middlesbrough will make a late decision on George Friend ahead of the visit of Chelsea on Sunday (20 November) after he picked up a knock in training.
Friend, 29, has been almost ever-present in Aitor Karanka's starting XI this season, completing 90 minutes in 10 of the club's 11 Premier League games this term.
The defender, who has captained his side for most of the campaign, suffered a minor knee injury in training this week with could threaten his place in the side when Antonio Conte's side come to town, with Dani Ayala also ruled out.
Karanka is also aware some of his players have arrived back at the club after long trips following the international break, with Gaston Ramirez and Cristhian Stuani having returned to South America for Uruguay's World Cup qualifiers against Ecuador and Chile.
"We have a few doubts in terms of fitness," Karanka said, the club's official website reports. "The players who were away have returned, but they have had long journeys. We also have Dani Ayala out, and we have a doubt with George Friend. Friend had a knock on his knee yesterday so we will need to check."
Middlesbrough have earned deserved draws against both Arsenal and Manchester City in the last month and Karanka is relishing another battle with a Premier League title challenger.
"It's another nice challenge for us," Karanka told a press conference on Friday. "To play against Chelsea in the way they are is tough.
"But we've worked hard to play these types of games, so it's another amazing one for us.
"Antonio [Conte] has done very well and is settling into the league very well. They are second within a couple of months and showing they are a really consistent team.
"I think they are really favourites to win the league, because they take advantage of not playing in the Champions League or Europa League."