O’Halloran joined Rangers from St. Johnstone on transfer deadline day on a four-and-a-half-year contract.
Johnstone, who played for Rangers in the 1970s and 1980s and is a club legend, believes that it is good for the former Bolton Wanderers prospect that he will not play at Ibrox today.
“Once O’Halloran beds in and gets up to speed at Rangers, he will be a really good addition to the side,” the former Scotland international wrote in The Glasgow Evening Times.
“He would, of course, have wanted to play against Kilmarnock this weekend but it gives him a chance to train with the squad and watch the game.
“He can get used to working with the players and the manager and get used to playing in the system. Then, come Monday, he will be desperate for the game at Alloa to come next weekend as he looks to get himself into the team.”
O’Halloran started his senior career at Bolton, and had spells on loan at Sheffield United, Carlisle United and Tranmere Rovers before moving to St. Johnstone in January 2014.
During his time at McDiarmid Park, the Scotsman, who can play as a forward or as a winger, made a total of 89 appearances and scored 16 goals.