Mauricio Pochettino says he is "not crazy" for believing troubled Chelsea are heading in the right direction, insisting it is only a "matter of time" before they enjoy success.

Pochettino's injury-ravaged side are languishing in 12th place in the Premier League after three defeats in their past four games.

Despite a huge outlay on players over the last 18 months, Chelsea have failed to keep pace in the race for a top four finish.

However, former Tottenham and Paris Saint-Germain boss Pochettino said he remained full of enthusiasm, regardless of his baptism of fire at Stamford Bridge.

"I think it's so exciting, this project," the Argentine on Friday. "We knew that it was going to be difficult and yet it's more difficult because of the circumstances, unexpected circumstances."

The 51-year-old pledged to fight for the struggling club, who were European champions under Thomas Tuchel just two years ago.

"I think the challenge is massive, but I really believe that we can succeed," he said.

"It's only a matter of time, but sometimes it's a lot to be patient and believe in the way that we are doing.

"The thing, of course, that is the most difficult thing in football is to keep believing when you don't get the results that you want. For me, (time) is not a problem. We will succeed. For sure, you will see.

"Maybe today you can say 'this guy is crazy', but I am not crazy. I know what I am doing."

Defenders Marc Cucurella and Reece James and goalkeeper Robert Sanchez joined the club's lengthy injury list this week, but France forward Christopher Nkunku could be in line for a debut against bottom of the table Sheffield United on Saturday.

Pochettino vowed that Chelsea would do all they can for injury-plagued skipper James, who only recently returned from a previous hamstring injury.

"We need to go in depth in the situation," he said. "He is a little bit down because he was very excited to come back and I think his coming back was perfect because it was step by step.

"That (injury) for him is difficult to accept. He's very disappointed, he's frustrated.

"Now we need to be careful in the way that we are going to talk, but to also assess and try to find the best solution for him to be consistent."