The England all-rounder is currently making a comeback from a fourth bout of surgery on his troublesome left ankle, which has repeatedly been unable to stand the strain placed on it by the hard-charging Lancashire pace bowler.
Although officials were prepared to play Flintoff in the four-day game, Lancashire were worried about him featuring in that match and their county championship opener against Surrey at The Oval starting on April 16.
Middlesex's Ed Joyce, one of four players with international experience in the party, will captain the MCC, the owners of Lord's.
Joyce's county colleague Owais Shah, who was on both England Test tours without playing this winter, is also included along with another man with Essex all-rounder Ed Joyce.
The squad also contains several players who have appeared for England Lions, the national A or reserve side, including Yorkshire leg-spinner Adil Rashid.
"It is an honour to be asked to captain the MCC team against Sussex and it's a match I'm greatly looking forward to," Irish-born Joyce said.
"With the spotlight on this game it's a chance for all of the guys to get some early season form and make the England selectors sit up and take notice.
"There will be a lot of determined cricketers at Lord's and you can expect a very competitive match as a result."
Former England batsman John Stephenson, now MCC's head of cricket, said the match offered a chance for players to make a name for themselves. "
"This happened last year when an outstanding performance from Adil Rashid was the catalyst for a very good season, culminating in him being voted the Cricket Writers' Club Young Cricketer of the Year."
MCC squad to play Sussex at Lord's from April 10-13:
Ed Joyce (Middlesex/ENG, capt), Ravi Bopara (Essex/ENG), Michael Carberry (Hampshire) James Foster, (Essex/ENG, wkt), Steven Finn (Middlesex), Arun Harinath (Loughborough UCCE and Surrey), Steven Kirby (Gloucestershire), Graham Onions (Durham), Adil Rashid (Yorkshire), Alan Richardson (Middlesex), Owais Shah (Middlesex/ENG), James Tredwell (Kent)