Mahmood yesterday took five for 76 against Sussex as both sides suffered batting collapses on the first day at Hove but still clearly believes his team-mate is ready to go back on England duty again.
Flintoff, after a handful of Twenty20 Cup cameos for Lancashire, started his first LV County Championship match since a thigh injury in early May, and managed 15 overs which yielded 43 runs but no wickets.
England's squad for the next Test series against South Africa will be announced on Thursday and the all-rounder, who took an easy catch, will now be looking to shine with the bat today, ready to go in next wicket down after his side ended the first day on 67 for four.
But Bolton-born fast bowler Mahmood, who won eight England Test caps in 2006 and 2007, modestly brushed off praise for his own performance in Sussex's total of 253 to recommend Flintoff to the national selectors.
He said: "All the boys bowled pretty well as a unit and we did well to keep Sussex down to that score on a wicket like that. It was flat and slow and didn't give us any help after they won the toss.
"But I'm very happy to end up with five wickets on the day, and Freddie bowled quick and aggressively and was hitting an area consistently. He's quite economical as well and an asset to any team.
"I'm not sure whether he's at 100% again yet but he looked pretty strong to me and I know he's pleased with how he went."
Mahmood was never going to publicly agree with the suggestion that much of his success on the day was due to a poor selection of shots by the Sussex batsman, although he admitted: "I didn't have anything like the rhythm that I've had when taking five wickets here a few times before."
Sussex opener Chris Nash was ludicrously run out, skipper Chris Adams dragged one on to his stumps and even top-scorer Robin Martin-Jenkins gave his wicket away cheaply after an impressive 70, attempting an outrageous pull shot to South African Francois du Plessis' overpitched ball which bowled him.
Wickets continued to tumble when Lancashire replied, Jason Lewry removing Paul Horton and Mal Loye in successive balls and Du Plessis going cheaply before a brilliant Carl Hopkinson catch saw off Lou Vincent for 38.