Andy Flower says England's Kevin Pietersen must look after himself

Kevin Pietersen

England boss Andy Flower says Kevin Pietersen must "look after himself as well as possible now" in order to extend his international career.

Pietersen, 33, is one of a number of England players engaged in all three formats - Tests, one-day and Twenty20.

The batsman described himself as an "old man" after his hundred in the third Ashes Test at Old Trafford.

"He's in his early 30s - everything seems to hurt a bit more after long days and big innings," added Flower.

Pietersen was only passed fit to play in Manchester at the last minute after overcoming a calf strain, and has missed three out of eight Tests this year because of injury.

Team director Flower, who played 63 Tests and 213 one-day internationals for Zimbabwe, knows from experience that the body begins to struggle with advancing years.

As well as highlighting the need to avoid overworking 31-year-old fast bowler James Anderson, Flower also hinted that he is keeping an eye on Alastair Cook.

The Test and one-day international captain may be only 28, but it seems he may be rested for some matches.

Flower added: "The players that play all three forms of the game, we do try to look after in as wise a way as possible.

"Kevin's one of those guys, so we do take him out of certain competitions when it's necessary. Just like we do with Jimmy Anderson and might do with Alastair Cook in the future."

With Friday's fourth Test at Chester-le-Street in mind, Flower hinted at a change in England's seam attack.

Anderson, Tim Bresnan and Stuart Broad toiled hard for little reward during Australia's lengthy first innings at Old Trafford.

Chris Tremlett and Graham Onions have been included in a squad of 13 for the Durham Test, and Flower said: "We're totally focused on winning this series, and they are in the squad for a reason and available to play.

"We are quite willing to be flexible on that front.

"We thought Tremlett's type of bowling was more useful at Old Trafford, and he was the spare bowler if anyone had gone down on the morning of the game.

"Up at Durham might be slightly different, and Onions has been in good form all summer."