MIDDLESBROUGH head coach Aitor Karanka is on the verge of signing a fourth Chelsea player with defender Tomas Kalas set to move on loan until the end of the season.

Karanka has already brought in Kenneth Omeruo, Patrick Bamford and Jamal Blackman this season, but a shortage of options in defence has prompted the Boro boss to dip into the loan market again.

Injuries to Damia Abella and Ryan Fredericks have left Boro short at right-back in particular. Emilio Nsue, who has filled in the role in their absence, is on African Cup of Nations duty with Equatorial Guinea.

Albert Adomah will also miss today’s FA Cup third round tie at Barnsley having been named in the Ghana squad for a seven-day training camp ahead of the competition that gets underway later this month.

Rhys Williams is likely to continue his comeback from injury this afternoon, but given the severity of his injury and the length of time out, Karanka is keen not to throw the versatile Australian into too much too soon.

Kalas, who can play at right-back and centre-back, spent the first half of the season on loan at FC Koln, but he will join Boro once his deal with the German club officially ends at the beginning of next week.

The 21-year-old has played 17 times for Czech Republic’s Under-21 side and once for the senior side, while he impressed at the end of last season when he played in Chelsea’s win over Liverpool at Anfield.

Kalas could debut in next weekend’s trip to Reading.

Today’s trip to Oakwell might be regarded as an unwelcome distraction as they look to stay within reach of leaders Bournemouth in the Championship, but Karanka is keen to supplement Boro’s league form with a run in the cup.

The Spaniard will make changes to his starting line-up, but does not expect his team to take their foot off the gas against the Tykes, who lie 16th in League One.

“When you are a team in a lower division you always have more motivation to win the game,” he said. “I have to transmit to the players that they have to play with the same motivation than them and play with our usual intensity and style.

“We know we are better than them, but we have to play in the same way as we do in the league. They are playing at home against a team in a higher division so we have to be at our best.

“I know how important the FA Cup is here, we tried to do our best in the Capital One Cup and we lost on penalties to Liverpool. Now it's the FA Cup and it's an important trophy here.

“I am going to put on the pitch – maybe not the best, because I have to try other things or give players an opportunity – 11 players thinking about winning the game.

“I enjoy these challenges. Everything is new for me in this country and in this league. For me, it is exciting to play on Boxing Day, against Liverpool in the Capital One Cup and in the FA Cup. I am really enjoying my time here.”

Former Boro players Ross Turnbull and Leroy Lita are likely to line-up for Barnsley today, who have only managed two wins in their last eight matches.

The Tykes lost striker Davante Cole on January 1 after his loan spell from Manchester City ended. Karanka had pinpointed the son of former Newcastle and Manchester United striker Andy Cole as Barnsley’s main threat having scored seven times since arriving from the Etihad Stadium.