Gilberto believes Arsenal's trip to Anfield on March 31 will decide who takes third spot in the Premiership.
Arsène Wenger's side were eyeing a late bid for second before Andy Johnson's injury-time goal consigned them to defeat at Everton on Sunday.
After a break for internationals, Arsenal return to Merseyside to face fourth-place Liverpool. The Brazilian international believes it will be crucial in determining the winner of the mini-battle between the two sides.
"It can be decisive," said Gilberto. "But we know when we play there it is always hard. We need to keep our shape and we need to put other things out of our minds. We can't afford to miss our concentration like we have in a few important games.
"At times like this we must stick together. Especially after the hard weeks we have had before.
"We have an international break now but afterwards I hope we will be very focused because have to be ready for the run-in to qualify for the Champions League."
Copyright 2015 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source 19 Mar 2007