James Anderson failed to take the field for Lancashire on Friday in what England will hope is merely a precautionary measure ahead of next month's Ashes series and not a prelude to a repeat of the 2019 campaign against arch-rivals Australia.
Anderson, the most successful fast bowler in Test history with 685 wickets, left the field on Thursday's opening day of their County Championship match against Somerset at Old Trafford with what officials said was a "minor issue".
The 40-year-old did not return on Friday as Somerset made 361 all out, with Lancashire 72-2 in reply at stumps.
England face Ireland in a one-off Test at Lord's next month before the first of a five-match Ashes series gets underway at Edgbaston on June 16.
In the corresponding 2019 Ashes opener at the Birmingham ground, Anderson managed just four overs before pulling out, having torn his calf playing for Lancashire.
With substitutes unable to bowl, his absence left a huge hole in England's attack as Australia won by 251 runs.
If England are concerned about Anderson, Australia will have noted their star batsman Steve Smith has yet to hit form this season for second division side Sussex.
Smith fell for just three against Leicestershire on Friday after making 30 on debut at Worcester last week.
Smith's arrival to play in three Championship fixtures for Sussex has led to criticism the club are aiding Australia ahead of an Ashes series where the tourists are set to dispense with traditional warm-up games.
Instead, Smith will join up with Australia for their World Test Championship final against India at the Oval in June before starting their quest for a first Ashes series win in England since 2001.
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