Enzo Fernandez was booed by sections of the Chelsea support as Morgan Rogers scored on his first appearance for Chelsea in a 3-1 win against Real Socieded.
Joao Pedro also continued his fine pre-season form with a double as manager Xabi Alonso offered a glimpse of what could be his blueprint for the season.
But the action was overshadowed by the reaction to Fernandez’s second-half appearance, less than 24 hours after Chelsea’s self-imposed transfer deadline had passed.
Fernandez had been keen to join Real Madrid earlier this summer before the Spanish club ended their interest.
His representatives later held talks with Manchester City, but no offer was made to meet Chelsea’s £120m valuation before Friday’s 17:00 BST deadline.
Fernandez was booed by some early arrivals at Stamford Bridge when his name was read out 45 minutes before kick-off.
Chelsea’s stadium announcer then opted against reading out the names of the substitutes shortly before the match, but there were audible boos when Fernandez came on in the 62nd minute.
Chelsea supporters appeared divided, with others responding by chanting his name.
Yet, it was a signal of Alonso and Chelsea’s backing when Reece James left the field he passed his long-time vice-captain the armband as usual.
Each touch of the ball was greeted by a mixture of boos and cheers, while some fans also celebrated when Fernandez was fouled.
It followed attempts by some supporters to move on from a saga that appears to have ended with Chelsea now expecting to keep one of their best players.
Others, however, remain unhappy with his perceived disloyalty, having come out publicly about his desire to move to Madrid, with his agent Javier Pastore also claiming he is underpaid.
It will be interesting to see how supporters of the Premier League’s other 19 clubs react to Fernandez, given his celebrations and social media jibes after Argentina beat England in a World Cup semi-final in July.
That will remain an issue whether he remains at Chelsea or Manchester City elect to revive their interest and attempt to reunite him with his former manager Enzo Maresca before deadline day on 1 September.
