Flintoff bowled 13 overs on the final day as England pushed for victory
England all-rounder Andrew Flintoff will miss the fourth Test against West Indies in Barbados on Thursday with a muscle strain in his right hip.
The 31-year-old had a suspected tear that severely hindered him in the drawn third Test in Antigua.
He will be reassessed over the coming days in the hope that he will be fit for the final Test in Trinidad, which begins on 6 March.
Spinner Graeme Swann is also an injury doubt because of elbow trouble.
Flintoff was clearly struggling in Antigua, but still managed to send down 17 overs in West Indies' second innings as the tourists chased victory.
A statement on the ECB website read: "He will be reassessed over the coming days in the hope that he will be fit for the final Test in Trinidad and the one-day series which follows."
Seamer Amjad Khan and all-rounder Ravi Bopara have been called up to the senior squad as cover and could play in the two-day warm-up match which begins in Barbados on Sunday.
A one-day practice game against an WIPA President's Select XI is next up on March 14 before a one-off Twenty20 international which precedes the 50-over series.
In only his third Test, Swann celebrated his maiden five-wicket Test haul in the first innings and then took three in the second innings as England almost secured a series-levelling victory.
However, the developing injury could make him doubtful for the next Test of the five-match series, which starts on Thursday.
There is also some concern about the fitness of left-arm seamer Ryan Sidebottom, which is another reason why the squad was expanded.
Flintoff looked uncomfortable as he recorded his second duck of the match having been dropped to number nine in the batting order on day four.
"He played the first Test and struggled a bit with his Achilles, he has had a chronic Achilles problem, and is getting back to full fitness," assistant coach Andy Flower said.
Kevin Pietersen suffered a hand injury in the final over of the third Test, but it is not thought to be serious.
The batsman was struck on the back of the right hand when fielding close to the wicket, but England's medical staff remain confident that the damage is merely bruising.