A titanic top-of-the-table clash is anticipated as London Three South West top guns Portsmouth and Old Tiffinians clash at Rugby Camp (3pm).
Both teams boast unbeaten records and the visitors lead only on points difference.
Senior coach Neil McRoberts accepts it is a big match, even this early in the campaign.
'This is a huge game for both teams,' said McRoberts.
'We had a terrific game at home against them last season and lost away to them.
'They were easily one of the best teams we came up against.
'It looks like it will be no different this time around.
'We know where their strengths are and must stick to our game plan to nullify them.
'Whatever the conditions we believe we have the players that can adapt to them.
'If it is wet then if necessary we have the ability to lock the game down.
'In drier conditions we have lots of attacking options outside.'
The home side welcome back Mark Ovens, who is preferred at full-back to Sam Olie.
Though the youngster has been superb in Ovens’ absence, the hosts have opted for greater experience.
Robert Lamberton is back at centre allowing Dan Gates to playa at twelve which is his more natural position.
McRoberts views the midfield as a key area where the game could be won or lost.
'We know Old Tiffians thrive on broken play and have some very powerful runners,' he outlined.
'Our aim is to keep possession and play the game on our terms.
'It is vital that we are rock solid in the middle, making sure our defence remains compact.
'Our first up tackles must be made.
'When their outside half gets the ball I want him to look up and see a wall of black and gold in front of him.'
McRoberts views the game as an opportunity to keep early momentum going.
'We have done well so far but it will be even better if we can make it five wins from five.
'If we are to achieve it then we must keep our concentration for the whole 80 minutes.'