And while head coach Lineen maintains he has been impressed by Jackson's form so far this season, he is adamant having competition for the No.10 shirt is only going to improve hime as a fly-half.
He said: "Ruaridh has had three games in a row and I've been really impressed with how he's played.
"He's got the line moving in both attack and defence. I've been really encouraged by both players and how they are pushing each other upwards. It's great to have two such ambitious tens.
"Duncan has come on and made an impact. He's a very confident lad and deserves a chance.
"This is a good opportunity to see him (Duncan] against a team like Munster."
Ireland full-back Rob Kearney will make his 100th appearance for Leinster against Edinburgh on Friday night in a side which also sees the return of eight-cap Johnny Sexton.
And despite Edinburgh's terrible start to the season, Leinster coach Joe Schmidt maintains they won't be taking the Gunners lightly.
He said: "Edinburgh has a pretty tough pack and a solid set-piece.
"You have to have your discipline right, because in Chris Paterson, they have a very accurate kicker; his kicking out of hand is very good as well. His counter-attack is also very strong.
"Tim Visser was named on the Magners League Dream Team last year and he has scored some very impressive tries."
Elsewhere on Friday night, Newport Gwent Dragons face the Scarlets in a highly anticipated all Welsh derby.
Scarlets boss Nigel Davis brings in Vernon Cooper and Josh Turnbull while Dragons captain Tom Willis returns to front row duty
And after the Scarlets came away with the bragging rights on two occasions last season, 48-cap Wales international Robert Sidoli says it's time the Dragons restored some local pride.
He said: "So far we have performed at home but we have had two rocky away games.
"We are lacking that bit of confidence away from home so we need to pick up the wins and get some momentum.
"Scarlets down here is a big fixture and they beat us twice last year so we need to get a win against them."
Other fixtures this weekend include high-flying Treviso facing Dai Young's Cardiff Blues and Connacht line up against Ulster in the Irish derby.
Welsh captain Ryan Jones is expected to return in the Ospreys' clash against Aironi.