Key discussed the future of Ollie Robinson, who possesses a one-year central contract, but had a disappointing tour of India.
Robinson struggled with a back injury in the only Test of the five he played, continuing a long history of fitness problems.
“We have been pretty clear with Ollie. When he is at his best he is a very good bowler,” said Key. “When he’s not, down at 78 or 79mph, he goes back into the pack.
“Generally he is someone who bowls better the more he plays, but we don’t always have that in international cricket. He has got to find ways to find rhythm quicker.”
Robinson’s Sussex team-mate Jofra Archer has been named in England’s squad for the T20 World Cup after more than a year out of international cricket with a recurrence of an elbow injury.
Archer could warm up for the T20 series against Pakistan by bowling a spell on one of the final two days of Sussex 2nd XI’s game away to Kent at Beckenham, starting on Tuesday.
The 29-year-old has been continuing his rehabilitation by playing club cricket in his native Barbados.
“He keeps sending me the YouTube clips of his batting, because I think he fancies himself up the order,” said Key.
“Jofra needs to build up his robustness, so his body can do what is required to be a fast bowler. Hopefully next year he can play some red-ball cricket.”
