Conor Gaston, who is affiliated to Dungannon, is named in the team but he is in the Phoenix Academy. Michael Allen, who won his first senior Ulster cap recently, will captain the side from outside centre.
Belfast Harlequins prop Richard Lutton will join Ballymena duo John Burns and Conor Carey in the front row.
Michael Shiels (Rainey Old Boys) and David Houston (City of Derry) will play their first games at this level after impressing for their clubs in the Ulster Bank League.
The back row of Conor Joyce, Dominic Gallagher and Neil Faloon is a dynamic one and they will face a difficult task against the abrasive Connacht loose trio.
Former Ireland Under-20 international James McKinney will be joined at half-back by his Queen's University team-mate Paddy Farrell.
Luke Marshall and dkipprt Allen will form an exciting centre partnership which should cause problems to the visiting defence.
Chris Quinn, who has been in good try-scoring form for Queen's this season, is joined in the back-three by the senior-capped Gaston and Ricky Andrew.
Banbridge prop Michael Cromie will join Ballymena players Andrew Warwick, Stephen Mulholland and Paul Pritchard in providing forward cover from the bench.
City of Derry scrum half Andrew Semple, and Johnny Burgess and Taylor Acheson from Malone, are the back-line reserves.
Commenting on selection, Longwell said: "We have named a fairly young side for this game but we thought it was the right time to give opportunities to some of the players who have shown good form in the All-Ireland League.
"The clubs in Ulster are doing well in their respective divisions and it is important to reward players when they are playing well.
"It gives us an opportunity to have a closer look at some of the players who have been on our radar. There are some interesting combinations all over the field so it will be intriguing to see how they get on."
The former Ireland international added: "Connacht are travelling with a quality squad, they will have a number of professional and development players involved so they will be very difficult opposition.
"But we will focus on our own game and hopefully we can put in a good performance."
Entry to Wednesday's game at Deramore Park, the home ground of Belfast Harlequins, is £7 for an adult or £10 for a family of two adults and two children.
ULSTER RAVENS (v Connacht 'A'): Ricky Andrew (Ballymena); Conor Gaston (Dungannon), Michael Allen (Belfast Harlequins) (capt), Luke Marshall (Ballymena), Chris Quinn (Queen's University); James McKinney (Queen's University), Paddy Farrell (Queen's University); Richard Lutton (Belfast Harlequins), John Burns (Ballymena), Conor Carey (Ballymena), Michael Shiels (Rainey Old Boys), David Houston (City of Derry), Conor Joyce (Malone), Dominic Gallagher (Dublin University), Neil Faloon (Armagh).
Replacements: Andrew Warwick (Ballymena), Michael Cromie (Banbridge), Stephen Mulholland (Ballymena), Paul Pritchard (Ballymena), Andrew Semple (City of Derry), Johnny Burgess (Malone), Taylor Acheson (Malone).