Nottinghamshire batsman Michael Lumb has been ruled out for at least the first month of the season due to injury.
Lumb was forced to undergo surgery on his arm after tearing a tendon while playing for the Sydney Sixers in the Big Bash, and the 35-year-old opener could be on the sidelines for up to three months.
"The surgery was necessary if we're going to see him back fully fit. This is a huge opportunity for players to impress, take advantage of the space in the team and step up," director of cricket Mike Newell revealed in a club statement.
"Greg Smith and Steven Mullaney will see this as a chance to get into our team and get our season started in the right manner."
Jake Libby will also miss the early stages of the campaign after surgery to repair his cruciate ligament.