Arsenal have made a key addition to their backroom staff by hiring a new head of sport science from London rivals West Ham United.
Andy Rolls will begin work with the Gunners next month after leaving the Hammers this week. Colin Lewin will remain the club's head of medicine.
Rolls leaves Upton Park following the return to action of striker Andy Carroll, who made his first club appearance of the season in Saturday's 2-0 win over Cardiff after being sidelined since the summer with a foot injury.
One of his immediate aims will be to help Arsene Wenger's side can maintain their title challenge by helping key players such as striker Olivier Giroud and defensive duo Per Mertesacker and Laurent Koscielny avoid long-term injury.
In a club statement, West Ham thanked Rolls for "his hard work and wish him all the very best for his future career."
They have replaced Rolls with former Anzhi Makhachkala head of physiotherapy Dominic Rogan, who spent six years at Everton helping David Moyes maximise the performance of the Toffees' small squad.