Wasim has missed the championship encounter at Wantage Road this week with his shoulder giving him more problems than expected.
He took painkillers to play in the Benson and Hedges quarter final at Surrey, but the Pakistan ace does not want to do that again - and needs to give the shoulder complete rest to make sure he does not suffer any more reaction.
If he is ruled out of a game Lancashire must win to keep up with the pace at the top of the Axa League table, former captain Mike Watkinson is poised to take his place.
But whether Wasim plays or not, all eyes will be on Flintoff's exploits once again.
The 20-year-old England hopeful smashed a first class career best 124 not out and put on 166 with fellow centurion and England reject John Crawley as Lancashire built a commanding second innings lead of 209.
Flintoff even overshadowed Crawley, outscoring him on the way to a 106-ball ton with 15 fours and two sixes. He put away Devon Malcolm for a six and a four in successive balls to move to 96, and then brought up his three figures with a huge six off spinner Graeme Swann.
It beat his previous best of 117 at Hampshire last summer, and he said: ``Maybe I should have gone on to make more in the first innings here, so I was determined to do it properly this time.
``It's nice to get a century, because you only really get noticed when you get big scores. I worked hard and played more steadily, although I didn't think I restrained myself.''
Crawley took 150 balls and stroked 16 boundaries - all along the deck - to reach 109, his highest score of the season so far.
``I've promised myself I'd get my head down and work as hard as I could,'' he said. ``It's a case of building up my scores until I get a stack of runs - because I know that's the only way I can force my way back into the England picture.
``It's my own fault, but if I can keep this sort of form up, it will hopefully benefit Lancashire every game.''
Lancashire, after conceding a 102-run first innings lead and then getting into trouble at 96-2 in their second, rescued themselves with Crawley and Flintoff's partnership, and they resumed today on 311-3.