Sussex have signed India's Cheteshwar Pujara and Australia's Josh Phillipe as overseas players after the release of fellow Australia player Travis Head.
Middle-order Test batter Head, 28, had been due to captain the county in the Championship and One-Day Cup.
But Head now has expanded international commitments and is also expecting his first child in the coming months.
Pujara, 34, will be available from the opening County Championship fixture against Nottinghamshire on 7 April.
The right-hand batter, who was left out of India's current Test series against Sri Lanka, is also set to feature in the 50-over One-Day Cup.
Wicketkeeper-batter Phillipe, 24, will join Sussex from June to play in both the T20 Blast and County Championship.
He will replace Pakistan wicketkeeper Mohammad Rizwan, 29, who is set to play from the second round of County Championship fixtures on 14 April through to at least Sussex's eighth T20 Blast group game on 10 June.
Rizwan, who will arrive from Pakistan's ongoing home series against Australia, is expected to feature in his country's rescheduled ODI series against the West Indies in June, curtailing a stay that was meant to last until July.
Afghanistan leg-spinner Rashid Khan, 23, is also set to return as Sussex's second overseas signing for the T20 Blast once his IPL commitments have concluded.
Sussex say a new County Championship captain will confirmed before the start of the season.