Ibrahimovic, 35, starred in his debut season for United, scoring 28 goals across all competitions.
Conversely, Rooney played a far less significant role for Manchester United, spending the majority of his time of the bench.
And Kallstrom believes his ex-Sweden teammate was the partially to blame for Rooney's troubles.
"It is clear, he [Ibrahimovic] is a huge star," Kallstrom told Cafe.se.
"He can go to Manchester United as a 34 or 35-year-old and instantly become the central figure.
"No disrespect to Wayne Rooney, he is their record goalscorer, but he turned into a parenthesis when Ibrahimovic arrived."