The visitors bossed possession in Pamplona and had the lion's share of chances - the best of which were passed up by Cesc Fabregas - but Osasuna held on to become the first team in La Liga to keep a clean sheet against Barcelona in almost two years.
The stalemate represented the first dropped points for the Catalan giants this term, and meant they failed to equal the record of nine straight wins at the start of a Spanish season.
Speaking at his post-match press conference, Martino said: "The draw is insufficient. We should have won, given the chances we created. We weren't accurate in front of goal.
"(But) I'm pleased with the team's performance.
"I would be concerned if there had been a decline in our performance. We tied because that's how it had to be. I don't think our level has dropped.
"In the first half we were missing that final pass. We were off by centimetres.
The clearest chances came from (Martin) Montoya's end. He got forward well, but lacked a bit of precision in his final pass.
"In the second half we had four clear chances and gave the opposition no opportunity to counter-attack.
"Osasuna are a dangerous team on the break, but they did not create anything of danger."
Martino opted to rest several first-team regulars at the start of a big week for Barcelona, who take on AC Milan at the San Siro in the Champions League on Tuesday before facing Real Madrid in the first Clasico of the season at the Nou Camp on Saturday.
Lionel Messi started on the bench after the thigh injury which forced him to miss two games for his club as well as Argentina's recent World Cup qualifiers, while Gerard Pique, Dani Alves and Alexis Sanchez were not included.
Ballon d'Or winner Messi was introduced in place of Xavi 14 minutes from the end but failed to convert either of the half chances which came his way, dragging a left-footed effort wide and then being unable to get his shot away from close range when played in by a dink over the top.
"We were planning on Messi playing between 20 to 25 minutes," Martino said afterwards. "I wanted to give Leo 20 minutes ahead of the games against AC Milan and Real Madrid."
There was a starting berth for Carles Puyol, however, for the first time in seven months, and the 35-year-old club captain slotted in seamlessly at the back.
Puyol, who underwent knee surgery in the summer, was quoted as saying on www.as.com: "I feel better every day. I'm happy with the way I feel, but not with the result. I want to contribute as much as I can, both on and off the pitch.
"We're in good shape and we're fighting for the same objectives."
The defender agreed with Martino that Barcelona had been below par in the final third.
"We knew it was going to be a tough game," he said. "It's a difficult ground to go to, and we had our chances and controlled the game. We lacked that final pass.
"We've picked up another point, and, despite going for all three, it wasn't to be. We controlled the game but weren't that sharp in the final third."
Looking ahead to the visit of Carlo Ancelotti's Madrid next weekend, Puyol added: "It's some way off. What you have to do is take one game at a time.
Now we're thinking about the game (against Milan) on Tuesday."