James Anderson faces a race to be fit for the start of the Ashes next month after it was revealed the England seamer suffered a low grade muscle tear to his right calf earlier this week.

England's all-time leading Test wicket-taker is seen as instrumental to their chances of toppling Australia but he pulled up while attempting to bowl during Lancashire's Specsavers County Championship clash against Durham.

The 36-year-old, who only returned to bat briefly with a runner and did not bowl for the remainder of the drawn game, underwent scans which highlighted the injury.

The England and Wales Cricket Board says his availability will be "reassessed on an ongoing basis" for the one-off Test against Ireland, starting on July 24 at Lord's, and the Ashes, which gets under way at Edgbaston on August 1.

However, he was not named in Lancashire's XI to take on Northamptonshire on Sunday morning while he will be absent for their Division Two clash against Sussex, starting next Saturday.

An ECB statement said: "England seam bowler Jimmy Anderson, who left the field during Lancashire's Specsavers County Championship match against Durham at Sedbergh School on Tuesday July 2 due to tightness to his right calf, underwent an MRI scan on Friday.

"The MRI confirmed that Anderson has suffered a low grade calf muscle tear. As a result of the injury, he will commence a rehabilitation programme with the England and Lancashire CCC medical teams.

"Anderson will miss Lancashire's next two Championship matches against Northants and Sussex.

"He will be reassessed on an ongoing basis regarding his availability for the Specsavers Test match versus Ireland at Lord's on July 24 and the Specsavers Ashes Series against Australia starting on August 1."