England coach says India deserved the win, promises to improve before Ashes after intense 2-2 series.
McCullum said India earned the victory in the final Test and praised their fighting spirit.
He said England will take time to digest lessons before planning for future improvements.
England dropped six catches in India's second innings, which proved crucial in the result.
McCullum said he’s proud of England’s fight and effort, even though they couldn’t win the series.
With time to reset, McCullum’s priority is now preparing England for the Ashes in November.