Milan have already played Barca twice this season in the group stages of the UEFA Champions League with the Rossoneri earning a notable draw at the Nou Camp in September before losing 3-2 at the Giuseppe Meazza last month.
Galliani believes Milan have provided a bigger test for the Catalans who recently beat Madrid 3-1 at the Bernabeu in El Clasico.
"We're not so far away [from Barca]," Galliani told La Gazzetta dello Sport.
"The greatest difficulty [Pep] Guardiola's team faced in the first part of the season was not Real Madrid, but Milan."
The reigning Serie A champions could improve their squad further in the January transfer window with the loan signing of Manchester City's unsettled striker Carlos Tevez.
All parties involved are keen for the deal to go ahead but the sticking point remains Milan's insistence that the player joins on loan first while City too will not budge on their desire to see the back of the striker immediately and permanently.
"I promised Carlos that we would wait until the last day of the window and there is no alternative," Galliani said.
"We made an offer for Tevez which consisted of a free loan with a purchase option and right of redemption for them. That is our proposal and it will not change."
Tevez is currently in his native Argentina having flown home without City's permission last month.
Milan are in the market looking for a striker after Antonio Cassano undwerwent minor heart surgery in November and was ruled out for the rest of the season.