London: Former England captain Michael Vaughan feels that tough days are ahead for Andrew Strauss-led England as they face Pakistan and India in Test series next year.

England start the year with a three-Test series against Pakistan in the United Arab Emirates (UAE) and four in India at the end of 2012.

"India want a piece of England after what happened here last summer and Pakistan, who they play in January and February, will also be desperate to win, given the recent history between the two sides. There is bound to be a period when England's form dips. People will knock them then but we have to be realistic and accept they will not match those levels all the time," Vaughan wrote in his column in The Daily Telegraph.

Vaughan said England have to accept the fact that they can't be winning everything.

"We saw them losing their cool on the field against India in October when things started to go wrong. They are the No.1 Test team but must acknowledge there are areas of their game they need to improve, starting with playing in the subcontinent," he said.

Vaughan feels Pakistan's ability to pick up 20 wickets will make England vulnerable.

"They have started strongly by picking a sensible squad for the Pakistan series made up almost entirely of the players who have served them so well. But what makes England vulnerable against Pakistan is they have the power to take 20 wickets, something you never felt Australia and India possessed during the Ashes or last summer," he said.

"Pakistan should also be looking at England and thinking they can catch them out in the first Test. England have two warm-up games before the Test series but at the moment the opposition is unknown. The standard will probably not be high and we saw in Australia last year how important it is to build up to a Test series playing good quality opponents," he said.

The former England captain feels Strauss' captaincy is exceptional but he needs runs.

"He will be sitting at home now wanting that Test hundred. He has not scored a century since the Gabba Test last November and that will be swirling around his head because you life becomes just that little bit easier as a captain if you have a hundred under your belt. I saw enough in his game last summer to know he is playing well enough, it is just whether the pitches in UAE will suit his batting. He has improved playing shots down the ground but he is still predominantly a player who scores his runs square of the wicket. The wickets are slow in Abu Dhabi and Dubai meaning you need to be able to hit hard and straight. But he is such a fighter with a strong mentality that he can overcome those issues," he said.