England skipper Terry was a notable absentee from the team sheet for Sunday's FA Community Shield at Wembley, while Ivory Coast hitman Drogba was also omitted.
Terry is understood to have tweaked his anterior cruciate ligament, which is at the back of the knee, and will be out of action for around four weeks meaning he will not be available for England's friendly against Germany.
Drogba, however, should return in approximately 10 days as his knee problem is a minor one.
Nevertheless, with Salomon Kalou, Andriy Shevchenko, Claude Makelele, Michael Ballack and Claudio Pizarro all struggling to be fit, not to mention both Glen Johnson and Florent Malouda picking up knocks at Wembley, Jose Mourinho clearly has plenty of concerns ahead of the season opener against Birmingham on Sunday.
When Chelsea were unable to call on key men such as Terry, keeper Petr Cech and Joe Cole last season, they lost ground in the title race to United.
It is a situation they cannot afford to repeat again this time around, particularly with key dates against Liverpool at Anfield on August 19 and then a trip to Old Trafford in September.
However, Lampard, who stood in for Terry as skipper at Wembley, insists the Blues are better prepared and stronger from the lessons of last season - with former Bolton defender Tal Ben Haim having deputised at the back against United.
"In terms of injuries, we are not in the best of shape. There are quite a few people in the treatment room, which is not ideal," said Lampard/
"But we are calling on a bit of character early and have got a very strong group.
"We all know our plans and our ambitions. We are all getting ready for it now.
"We have got a strong team with a lot of personalities and have a lot of experience from years gone by. The players we have brought in also have experience, so we can go into the season with confidence."
Lampard added: "We have got more cover for John now than last season. I think Ben Haim did very well.
"Hopefully we will not miss John that much until he can be fit. Hopefully, that will not be too long because it is quite a small injury in terms of his knee.
"The strength John has got in himself, I am sure he will be back out there in a couple of weeks.
"We are all upset if we have got major players who are not playing - but you cannot cry about it, you just have to deal with it."
Mourinho was pleased enough with the efforts of his depleted side on Sunday, having drawn themselves level through summer signing Malouda before eventually losing on penalties.
"We put in a good performance against United without a recognised frontman for most of the game, and without the captain," said Lampard, one of three players to see a spot-kick saved by Edwin van der Sar.
"We lost on penalties, but they can go either way and we can still look to next weekend with confidence.
"We were pretty pleased with the performance as a whole.
"We can get better and will get better."
Lampard, however, knows there will be little margin for error when the business starts for real next weekend.
"You cannot afford to sleep," said the midfielder, himself playing through the pain barrier following a broken toe suffered on the trip to America.
"This year is going to be more competitive than ever. The big four are there ready for a good start. You cannot afford to fall behind, it is as simple as that."
Lampard added: "There will be that feeling of trying to get something back that we want.
"We had it fairly easy for a couple of years where we won comfortably. Now it is a great challenge to all of us to try to win it back."
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