Demba Ba could be followed to Chelsea by Taison, Micah Richards and Radamel Falcao

Chelsea will insist that Demba Ba undergoes a medical in spite of the Newcastle United striker’s chronic knee problem, with the club eager to register him in time for Saturday’s FA Cup tie after last night’s shock league 1-0 defeat to Queens Park Rangers.

Rafa Benitez’s players were booed at Stamford Bridge following their first home defeat in almost 30 years to their west London rivals. There were suggestions that Ba was in the stadium after Alan Pardew conceded that the player had left to join Chelsea “with our blessing” following complicated negotiations over his financial package.

Benitez refused to discuss Ba specifically but said: “The club is working and hopefully we will get someone else. If we can do the business then hopefully he’ll be available for the weekend.”

The club hope that Ba will be available to play against Southampton in their FA Cup third round tie on Saturday. In order to do so he will have to be registered by Friday lunchtime. He did not train yesterday once Chelsea had met his buy-out clause of £7m, which was confirmed by Newcastle.

Benitez defended his decision to rest Juan Mata, Ashley Cole, Ramires and Eden Hazard , after Shaun Wright-Phillips’ goal for QPR left Chelsea 14 points behind leaders Manchester United who have played one game more.

Benitez said that to be credible challengers for the title his team would have to be “almost perfect now”. He added: “It’s more difficult now, but I can’t be thinking about how many points we need. I have to think about the next game. It’s difficult for us now as we’re playing so many games with a small group of players. You could say that [tonight] they couldn’t get to the right level.”

Chelsea hope to add to make more than just the Ba signing this window with Brazilian midfielder Taison, at Metalist Kharkiv, on their radar. There were even suggestions last night that they could move for the Manchester City defender Micah Richards, currently injured, although Benitez dismissed that prospect.

Ba failed a medical at Stoke City in January 2011 and the club passed him over that month when he subsequently signed for West Ham who did not subject Ba to a medical. In spite of those problems he never missed a training session through injury at Newcastle and has played 54 Premier League games for the club since he joined them in the summer of last year, scoring 29 goals.

The entire deal for Ba could potentially cost Chelsea more than £20m with around £15m in wages, at £80,000-a-week over four years, a further £7m to meet the buy-out clause, £2.5m which is being divided between Ba and his representatives. The deal has been squabbled over by different parties claiming to represent the player who has negotiated through his friend Alex Gontran.

The sale of Daniel Sturridge to Liverpool went through today, bringing in £12m for Chelsea. Although it is a good financial return, it leaves them short in attack with their big signing, the Colombian striker Radamel Falcao expected to happen in the summer. The club have never ruled out a move for Falcao from Atletico Madrid this month, if it could be done but there has been a general acceptance that it will be easier to do in the summer.

Officially presented as a Liverpool player today, Sturridge said that he had joined a “humungous” club. The 23-year-old said: “I am humbled and happy to be here. Brendan Rodgers said he sees me here for a long time - and I also see myself here for a long time. I've not signed here to play for a couple of years and then move on.”

Benitez said that Petr Cech was still “two to three weeks” away from playing. John Terry is still yet to train with the first team and no date has been set for his return. He has bruising to the bone in his knee.