Mourinho doubt over Del Horno dedication

Mourinho is understood to be extremely disappointed with Del Horno's progress since the 24-year-old injured his thigh in the Premiership match against Sunderland on 10 September and sources at the club say that the Christmas period will be a critical time for the player's relationship with his manager. His poor form is likely to mean he starts as a substitute against Fulham today, although Damien Duff could return following an Achilles problem - Duff is set to be handed a place on the bench.

An £8m signing in the summer from Athletic Bilbao, Del Horno is also the first choice left-back for Spain and began the season in exceptional form for Chelsea, playing in the first five Premiership matches. However, after injuring his thigh, he missed a month's football and there have been concerns about him since.

While Mourinho has not considered selling the player, he is said to have misgivings about the length of time it is taking him to settle into English football. He believes that Del Horno has struggled to adapt to the demands of playing for the Premiership champions and Mourinho's concerns are well known among the club's back-room staff.

Mourinho keeps a very close eye on the individual progress of all his players, whether they are fit to play or not, and his attention has been drawn to the length of time it has taken Del Horno to recover his form. After overhauling the medical department at Chelsea last summer, and bringing in the former UK Athletics doctor Brian English, Mourinho has been full of praise for the work done in bringing players back to fitness more quickly than before.

However, he has been unimpressed at Del Horno's attitude to rehabilitation and, in an echo of the criticisms directed in private at Arjen Robben last season, Mourinho feels that the left-back has not done enough to regain his fitness quickly. Robben fell out of favour with his manager at the end of last season when he refused to start in the first leg of the Champions' League semi-final against Liverpool because of an ankle injury.

Robben also picked up a knee injury against Real Betis on 1 November and, despite being cleared to play by the club two weeks later, delayed his return to training for another week in a move that did little to strengthen his relationship with Mourinho. The Chelsea manager uses players such as Frank Lampard and John Terry as examples when asking individuals to play through the pain or hasten their return.

Unlike Robben and Del Horno, Terry continued to play last season despite a bone spur on his left foot. He had to endure painkilling injections before training and matches and, at one point, the spur, which grew off the main toe bone, actually punctured his skin. Despite the agony of his nerve being exposed, Terry waited until the title was sealed before having an operation.

There are fears that Del Horno has started to make his own diagnosis about the state of his fitness, which represents a problem for Mourinho who does not feel Wayne Bridge is ready to be his first-choice left-back. The England international, who broke his ankle in February, has only made one appearance since regaining fitness and could yet go on loan to Fulham or Newcastle in January.