Pjanic has featured 11 times in all competitions since arriving at Camp Nou in June for an initial €60million, with Arthur moving in the opposite direction in a separate arrangement.
He has started only once in LaLiga, however, the Bosnia-Herzegovina international's other five appearances in the competition coming from the substitutes' bench.
And ahead of Wednesday's (AEDT) UEFA Champions League clash against former side Juve, Pjanic conceded it is difficult to accept being used as a back-up player.
"Honestly, I don't understand the reason of this situation. I want to play more, I know I can give a lot," he said.
"When the coach called me, I was always ready. I did well, I played good games. More than that, I do not know what I could do. I'm training, I'm ready.
"I am not satisfied and I cannot be satisfied. During my career I have never accepted the idea of not playing and I do not accept it now."
Pjanic has been a regular in the Champions League and impressed in last week's win over Ferencvaros, his 134 attempted passes the most of any player in this year's competition.
But he was back among the substitutes for Sunday's (AEDT) LaLiga trip to Cadiz, playing only the last 13 minutes as Barca fell to a shock 2-1 loss.
"We will see what happens," he said. "I am ready, I train well and I wait, I cannot do anything else. It is a very delicate situation that does not suit me."
Pjanic now faces a reunion with Juventus, where he won four Serie A titles in four seasons before making the switch to Catalonia earlier this year.
He averaged 48.35 passes per 90 minutes in the opposition half in his final season in the division, second only to Napoli's Fabian Ruiz (50.64) among players to have featured at least 10 times.
The 30-year-old also represented Roma in Serie A for five seasons and said he misses life in Italy.
"I had a great time at both clubs. It's where I spent important seasons," he said. "My nine years in Italy was very nice. Honestly, I miss it.
"Now I have this new challenge in the biggest club in the world. I wanted to try it, I am satisfied with the club and my team-mates.
"Juventus have remained in my heart - I follow them whenever I can.
"The draw made me happy. Too bad I could not play in front of the fans in Turin, but there will be other opportunities. I wish Juventus the best, but tomorrow we want to win."
Juve lost the reverse meeting with Barca 2-0 in September and has won only one of its three previous away Champions League meetings at Camp Nou.