Saqib Mahmood will visit a specialist in London next week amid concerns that a stress reaction in his back could rule him out for the rest of the English summer.
Mahmood, who has played for England in all three international formats, has only played five games for Lancashire this season, two in the County Championship and three in the T20 Blast.
He has not played at all in the last month due to injury and ESPNcricinfo understands there is concern that he could miss the rest of the season, including Lancashire's Blast and Championship campaigns and the Hundred, where he is under contract with Oval Invincibles.
Lancashire anticipate that his consultation at the start of next week will provide a clearer indication on the exact nature of his injury and the timeframe for a potential return. The club declined to comment when contacted.
Another injury would be a cruel blow for Mahmood, who missed all but one game of the 2022 season with a lower-back stress fracture which was diagnosed weeks after he made his Test debut for England in the Caribbean.
He made his competitive comeback for England Lions in Sri Lanka earlier this year, and was then part of the ODI squad on England's tour to Bangladesh, returning figures of 0 for 41 from his nine overs in his only appearance.
There is some positive injury news for Lancashire, with Richard Gleeson included in a matchday squad for the first time this season after a wrist injury ahead of Friday night's fixture against Derbyshire. Steven Croft also returns following a calf injury.
Lancashire sit fourth in the North Group of the Blast as the preliminary stages approach their climax, with a game in hand on third-placed Nottinghamshire. All three of their remaining fixtures are at Emirates Old Trafford, where they have a 100% record this season.