Sussex's leadership of the County Championship will be under threat from England's premier fast bowler at the Riverside this week.

Steve Harmison will continue his comeback from injury for Durham after he was left out of England's squad for the second Test against Sri Lanka which starts on Thursday.

The 27-year-old had to return home early from England's winter tour of India because of a shin injury.

He made his comeback in last week's drawn Championship match against Nottinghamshire and took two wickets in 25 overs.

But he did not bowl on Saturday during a rain-affected final day.

If Harmison comes through against Sussex, starting tomorrow, he should return to England duty for the third Test at Trent Bridge next week.

Chairman of selectors David Graveney said: "The selectors feel it is prudent for Steve to play a little bit more cricket for Durham and we will monitor that.

"Although he is fit it is questionable whether he is match fit."

Sussex cricket manager Mark Robinson believes his side face their toughest game of the season - even without the Harmison factor.

Eight of the squad who took Sussex to the top of the table with a third win in four games were given last week off.

Robinson is banking on his senior players to return fresh and ready for another intensive period of 21 days in the next 26 days.

He said: "The danger signs are there because we have allowed the players to have a break. I'm trusting that they will come back and be ready to play.

"There is a danger that you take a break and find it hard to pick things up again.

"But they are an honest bunch and I don't think there will be any problems.

"Teams are going to start targeting us now because of the start we have had and they will be looking for the bubble to burst. I'm hoping it won't be in this game."

The county have made their best start to a Championship season since 1960 which makes a nice change from the last few years when Sussex have been slow out of the blocks before finding their form in the second half of the summer.

Robinson added: "We have only achieved one thing so far which is making a good start.

"But I have learned is that is is easier to win games when you are looking forward rather than being worried about the threat of relegation and thinking before every game that you have to get something out of it."