Chelsea set to capture £21m David Luiz

London club may sign defender today but Benfica's demand for player in exchange could be an obstacle.

Chelsea are confident they will complete the signing of David Luiz from Benfica for a fee of £21.5m within the next 48 hours. Representatives from the Portuguese club, including president Luis Felipe Vieira and Luiz's agent, Giuliano Bertolucci, flew to London on Saturday to discuss terms with the Chelsea chairman, Bruce Buck, and chief executive, Ron Gourlay.

Although the Portuguese delegation returned to Lisbon without a deal being completed, it is understood progress has been made. The two clubs are to continue talks today, and a deal is expected to be concluded within days. Luiz was omitted from the Benfica team for Saturday night's 4-2 home win over Nacional in the Portuguese Liga.

The deal could be done today before Chelsea's Premier League game at Bolton Wanderers, where Carlo Ancelotti's side will be without midfielder Frank Lampard, who has a calf strain and has not travelled with the squad. Club sources said last night the 32-year-old is expected to be fit to face Everton in the FA Cup next weekend.

The signing of Luiz (left) will be the west London club's biggest move in the transfer market for almost five years, since they spent £30.8m bringing Andrei Shevchenko from Milan in July 2006. Luiz will be the most expensive defender in the club's history, and will become the fifth player to be signed for more than £20m, following Shevchenko, Didier Drogba, Michael Essien and Shaun Wright-Phillips.

The main stumbling block concerns Benfica's desire to include a player in exchange, in addition to the £21.5m fee.

The Portuguese club want one of Chelsea's young players, such as left-back Patrick van Aanholt or centre-half Jeffrey Bruma, on a permanent deal. Chelsea, however, are interested only in a loan arrangement until the end of the season.

Ancelotti has high hopes for both Van Aanholt and Bruma, and is not happy with the thought they might be used as a makeweight in the Luiz deal.

Benfica have also enquired about the availability of striker Salomon Kalou, but Chelsea are ruling out letting the 25-year-old Ivory Coast international leave under such terms.

The Premier League champions, however, would consider releasing one of the two Serbian players who are currently on loan at Dutch side Vitesse Arnhem – midfielder Nemanja Matic and defender Slobodan Rajkovic.

Benfica claim they need a new player to cover the loss of Luiz, but they have already signed a possible replacement in the Brazilian Jardel.

Luiz, 23, will line up in defence alongside John Terry, although he can also play at left-back. Luiz began his career as a defensive midfielder, but was converted to a centre-half at Vitoria, Brazil. He was signed by Benfica in January 2007 as replacement for Ricardo Rocha who left to join Tottenham Hotspur.

Luiz has been Ancelotti's priority for some time, and his arrival will make up for the disappointment of losing out to Tottenham last week for the £3m signature of midfielder Steven Pienaar.

Benfica rejected two bids from Chelsea for Luiz earlier this month, but a slight setback to Alex recovery from knee surgery, ruling out the Brazilian until the middle of February at the earliest, prompted the London club to redouble their efforts.

Benfica had initially valued Luiz at £38m but financial pressure at the club has left them resigned to taking a much lower offer. The arrival of Luiz will bring down the average age of the Chelsea squad, although Ancelotti denies suggestions that the champions are beyond their sell-by date. He said last week: "Do you know what is the oldest team in the world? Inter Milan, 29.6 years average age. Another question – who was the winner of the Champions League last year? Inter Milan. We are not the oldest because the oldest is Inter. If you mention Terry, Lampard and [Didier] Drogba, I would like to continue to have this kind of player. We can mention [Branislav] Ivanovic, we can mention Ramires, we can mention [Daniel] Sturridge, we can mention [Josh] McEachran."

Chelsea hope to have Luiz in the squad in time for Saturday's FA Cup tie at Everton. Although Lampard misses tonight's trip to the Reebok stadium, captain Terry returns after passing a fitness test on his back injury.

Who might Chelsea be willing to swap?

Jeffrey Bruma (Age: 20)

Highly rated Dutch centre-back who has one international cap. Joined from Feyenoord aged 15 and, after making his first-team debut in 2009, his first start came in 4-3 League Cup loss to Newcastle. Struggled in recent 3-3 draw with Villa and a loan move could offer experience.

Patrick van Aanholt (20)

The Dutch left-back's playing style has been likened to Ashley Cole. The player more favoured by Benfica, who want a permanent move – something Chelsea have ruled out. Joined Chelsea from PSV in 2007 and has spent loan spells with Coventry and Newcastle. Yet to start a league game with for the Blues.

Nemanja Matic (22)

Tall Serbian central midfielder, who moved to London in a £1.5m move from Kosice in 2009. On loan at Dutch club Vitesse Arnhem, although Chelsea have the option to recall him this month. Short of first-team chances at Stamford Bridge with the midfield well covered.

Slobodan Rajkovic (21)

Centre-back in the same mould as his compatriot Matic and has been capped four times. 6ft 3in defender joined for £3.8m as a 16-year-old in 2005 from OFK Beograd. Had loan spells at PSV, FC Twente and now at Vitesse. Chelsea may consider allowing him to join the Portuguese side for the experience.