O'Neill opted to stick with the same starting line-up for the three league games in eight days which brought victories away to Manchester United and Sunderland and then at home to Stoke at the weekend.
But Petrov feels the players currently outside of the first choice XI can be brought into the equation without weakening the team if O'Neill feels he has to freshen up his side.
John Carew demonstrated the strength in depth by replacing the injured Emile Heskey and scoring the winner against Stoke, while midfielder Steve Sidwell also impressed when he replaced Stewart Downing.
Petrov said: "I think we are making the manager's job even harder. John (Carew) comes on and scores the winner against Stoke and Steve (Sidwell) could have had a hat-trick even though he only came on for 15 minutes.
"We are all working for the team. It is very frustrating because every one of us wants to play, which is natural for every footballer, but we know only 11 can start.
"It is good that we have people on the bench like Nigel Reo-Coker and Habib Beye who could easily walk into the team if the manager decides to pick them.
"That is great competition that can make us stronger.
"I think the manager excepts we might need to rotate, he knows that. That is why we have so many players and we have got two teams equal here now so he can rotate without worrying about getting weaker."
Petrov believes O'Neill may decide to try and strengthen the squad during the January transfer window despite its current depth in terms of quality.
The Bulgarian international said: "It is definitely strong but Martin O'Neill always tries to improve the team and the chairman (Randy Lerner) has been very supportive to the manager.
"I think if he adds something, it will be good for the team. It is a strong squad but the manager knows things change very quickly in football, injuries, suspensions.
"We will see. It will be interesting because, not just us, but other teams will try to strengthen as well so I hope we can get even stronger."
Arsenal 8/11, Draw 5/2, Aston Villa 4/1