The Blues travel to the Gtech Community Stadium looking to return to winning ways after being held to a 2-2 draw by Hull City at Stamford Bridge last weekend.
There had been concerns surrounding João Pedro after the forward withdrew from Brazil’s squad because of an injury. However, Alonso has not ruled him out of the Brentford fixture and will make a final decision after the team’s last training session.
Reece James is also being monitored after missing part of Tuesday’s training. Alonso explained that the captain’s situation would be assessed before the squad is selected.
Moisés Caicedo is another player whose availability remains uncertain. The midfielder has been recovering from a recurring calf problem, but Alonso revealed that he is getting closer to a return and could potentially be involved against Brentford.
The Chelsea boss was also asked about Marco Palestra and Jordan Henderson, who are yet to make their competitive debuts for the club. Alonso again stressed that decisions on the squad would be made after the final training session.
Chelsea will therefore head into Friday's derby with several players still being assessed, meaning the final squad and starting XI are expected to become clearer shortly before kick-off.
The match at Brentford is scheduled for Friday evening, with kick-off at 8pm BST.