Crystal Palace skipper Shaun Derry has tipped new signings Freddie Sears and Darren Ambrose to have a big impact at the club - but warned the Eagles they need to continue to strengthen if they are to challenge for promotion.

Sears, who joined on a season-long loan from West Ham last month, and Ambrose, who signed a two-year deal on Thursday, trained with their new team mates for the first time last week and captain Derry revealed he was impressed with what he saw.

"They have settled in really well," said the 31-year-old.

"We all know what Darren Ambrose is about but we don't really know too much about Freddie Sears other than the reports everyone else has read.

"He has probably never worked under a manager like what we have in Neil Warnock and I am sure he will have a really enjoyable season here and Darren will want to get back to the good form he showed a few years ago.

"Both of them have looked very fit lads but when the balls come out you can see they have got talent."

With Alan Lee set to join Shefki Kuqi and James Scowcroft out of the Selhurst Park exit door, Palace are struggling for numbers upfront and Derry, who has been given the green light to return to training following a shoulder operation, believes they need more numbers and soon.

"I think we do need more upfront," he said.

"You look at the two teams that went up automatically last year and they had quality in the frontline and had a number of strikers to pick from.

"We all know there are restraints on the money side at Palace so if we can do deals one way or another that's the way it has got to be."

The Eagles fly out to America for their pre-season tour on Saturday and Derry is hopeful the increased exposure can gain them a whole new set of fans.

"We are going there for two reasons," said the former Leeds man.

"We are going out there to get fit and play a couple of games but also to try and spread the word about what Palace is all about.

"If we can get some fans from the other side of the Atlantic the better it will be for us."

Crystal Palace next three friendlies: Tomorrow Boreham Wood (a), July 13 Crystal Palace USA (a), 16 Harrisburg City Islanders (a).