Three points separate the lead pair, who have each won nine of their 11 matches, Portsmouth suffering a surprise defeat by mid-table Totton & Eling last week.
Sarisbury send an unchanged side into the fray, while Portsmouth (who won the first meeting between the sies at St Helen's) remain without strike bowler Steve Warner for the rest of the season.
Sarisbury Athletic: Franklin, Morton, Cookson, Lovett, Robson, Feltham, Williams, Pascoe, Clark, S Hill, Rawlins.
Portsmouth: Duggan, Joy, Ashraful, H Gadd, Wimble, Daini, Kooner-Evans, F Gadd, Eales, Lewis, Rao.
Third placed Hook & Newnham Basics host an Andover side in serious relegation trouble after only two wins in 11 matches.
Hook: Warner, Lockwood, Neville, M Buckingham, Armstrong, James, Webster, J Buckingham, Gardner, Murrell, Divecha.
Waterlooville and Rowledge both parade full strength teams at Rowlands Avenue.
Waterlooville: Reynolds, McGregor, McBride, McCoy, Robinson, Shephard, Jackson, Birch, Silva, Hillman, Mitchell.
Rowledge: Ben Wish, Ollie Baker, Jonty Sebborn, Zac Le Roux, Max Martin, Justin Felsch, Olly Ryman, Will Ryman, Ryan Littlewood, David Lloyd, Ed Reilly.