Coach Mark Robinson has told Sussex’s fringe players they must follow the example of Luke Wells and become more ruthless.

Robinson faces a selection dilemma for tomorrow’s County Championship clash against Yorkshire at Hove with four first choice players unavailable.

The batting line-up is the main cause for concern with Matt Prior is playing in the first Test against Sri Lanka at Cardiff, Luke Wright is recovering from a knee injury and Ed Joyce on international duty with Ireland.

Fast bowler Rana Naved is also ruled out after returning to be with his family in Pakistan which is a huge blow after he took ten wickets in the victory over Somerset last week.

Ben Brown and Joe Gatting both made centuries in the three-day match against Oxford University this week to stake their claims for the vacant batting spots while formerNew Zealand international Lou Vincent is another option and offers more experience.

Both Brown and Gatting had opportunities in the side earlier in the season but were unable to make the most of them while Wells has scored two centuries to make the No.3 spot his own.

Robinson said: “What you want is for someone to do what Luke Wells has done and make it almost impossible to leave them out.

“Joe made a 90 and Ben a 60 in the first game of the season but I don’t think they can feel hard done by because the bottom line is neither of them went on to convert them into big hundreds.

“Both of them probably feel they deserve another opportunity after making hundreds at Oxford but I was disappointed neither of them went on to get a big one. They both made centuries before lunch and had a chance to really push on and take the selection out of my hands rather than make it a case of which one to go for.

“We are trying to preach to people that they have got to be more ruthless and greedy. I wanted them to be moaning that we had declared when they were on 200 or something like that.”

Naved Arif is favourite to replace Rana but Chris Liddle and Lewis Hatchett are also in contention while Ollie Rayner could play as a second spinner depending on conditions.

Robinson is still weighing up whether to rush Joyce back from Belfast on Monday night after playing in the second of two one-day internationals against Pakistan – who will feature Sussex’s Twenty20 signing Umar Gul.

Joyce is averaging just under 60 in the Championship this season and has formed a prolific opening partnership with Chris Nash but the logistics of getting him back in time for the start of play on Tuesday have not been finalised.

Robinson added: “There is still the option of playing a replacement for Ed but it depends on a number of factors.

“It is going to be a fairly inexperienced team in the same way as it was at Liverpool and Durham at the start of the season but there is plenty of potential there and it will be a case of people taking more responsibility.”