The Ivory Coast star left the Blues for Chinese Super League outfit Shanghai Shenhua following their Champions League success in May.
Chelsea owner Roman Abramovich has spent heavily to cover the departure of the 34-year-old, bringing in Eden Hazard and Marko Marin along with Oscar.
Ramires believes that the big-spending European champions will help the club fight for trophies on all fronts in the new season.
"This preparation period has been great to make the team gel and make the player become fit," Ramires told Lancenet.
"We lost some key players like Drogba, but we signed some talented players like Oscar and [Eden] Hazard, so we didn't lose strength.
"I am confident that we will have a great season, but the truth is that in football you have to produce on the pitch. We will keep working to be in condition to produce our best when the season starts."
Oscar is part of Brazil's Olympics squad and will not have the chance to meet his new team-mates until the Games are over next month.
His arrival means the Blues now possess four Brazilian players in their squad and Ramires hopes it will end talk that South American stars are not suited to the rigours of the Premier League.
"The confirmation of the signing of Oscar made us very happy. As far as David Luiz, Lucas Piazon and I are concerned, he will feel at home from his first day at the club," he added.
"It is good that the perception of Brazilian players not being able to adapt to English football is changing.
"I am sure Chelsea will be very beneficial for Oscar's career and he will help us a lot to fight for titles. We are here to help him in what he needs."
