Kevin Pietersen admits England will have to play at their best to remain top of the ICC Test rankings this summer.
Pietersen concedes England received a wake-up call with their 3-0 defeat by Pakistan followed by scrambling to a 1-1 series draw against Sri Lanka.
Skipper Andrew Strauss' side have to face the West Indies before the eagerly awaited series with number two ranked side South Africa.
Pietersen said: "It was a hell of a difficult winter. To come under pressure from a very good Pakistan side, we realised we weren't as good as we thought we were.
"I'm not saying we thought we were this most incredible outfit, but we had played some very good cricket and it was nice to come under a bit of pressure.
"It is never nice to lose but good that we realised we've got some work to do, especially in the sub-continent.
"We have started doing that and it took a little bit of time. The hard work the guys consistently put in proved fruitful in the last test (against Sri Lanka). It was great to finish that way."
Pietersen admitted: "It's a lot harder to stay at the top than to get there. A lot of people don't want you there and the pressure at the top is huge, the weight of expectation is massive.
"But we've got that tag going into the summer here so we will have to play some very good cricket to keep that tag. Can England stay number one? If we play to our best, most definitely."
Pietersen is anticipating a classic battle against South Africa between two finely balanced attacks and knows the quality of the opposition from his recent spell in the Indian Premier League.
He said: "We probably edge the attack with Graeme Swann in our side but I played with Morne Morkel for the past month in India and played against Dale Steyn in Delhi the other day.
"They are world-class bowlers and our batters are going to have to make sure they deal with whatever comes up against us - but so will their batters because our attack is pretty special."
The heartening news for England is that Pietersen feels in prime form, even though he was confined to a fielding role when in action for Surrey on the opening day of their away clash with Worcestershire.
He said: "I feel like I've never batted better. I feel in great nick at the moment but everyone knows you have a couple of bad scores and everyone says you are in bad nick again.
"I know that is not true but all I'm doing at the moment is concentrating on my batting, doing whatever I can do to influence a fixture here in Worcester.
"I'm at the stage of my career now where that's all I want to do, just influence games positively and play to the requirements of the team and whatever happens, happens."