Buchanan said his batsmen only had themselves to blame for letting India seize control of the match after a dramatic fourth at Adelaide Oval.
"I think India put the ball in the right areas but some of the shot selection showed a bit of immaturity," Buchanan told a news conference.
"Any team can be bowled out for 196 if the opposition are bowling exceptionally well and the conditions offer that but I don't think we can seek excuses from that today."
Australia looked to have the match in hand after they racked up a massive first innings total of 556 before India replied with 523.
After the home side's collapse India were left needing 230 for victory, a target they reduced to 193 after reaching 37 without alarm by stumps on Monday.
"Part of our batting is always to keep the scoring rate going and score as many as you can but nonetheless there's still a maturity about how you go about doing that," Buchanan said.
"I don't think our top six chose the best way to go about doing that."
Buchanan said Australia had planned to bat until lunchtime on the final day, then try and bowl the Indians out as the wicket deteriorated.
"Obviously the odds are in India's favour and there wouldn't be too many people expecting the result to go the other way," he said.
"Obviously we'd like to be in a better position than we are but I think what you'll find about this side is that they're not going to give in and 193 is still a few runs to play with.
"The wicket's starting to play a few tricks and there'll be a few more so I wouldn't rule us out at this stage."
Indian seamer Ajit Agarkar destroyed the Australian batting lineup to finish with career best figures of six for 41.
The 26-year-old said the tourists were confident of going on to seal victory on the final day.
"They've still got a lot of runs and we still have to get them but we're very confident, we've got a great opportunity here," he said.
"If we're patient and keep our heads we should get the job done.
"Both teams had an equal chance but early wickets was always going to be the key. We knew if we picked up two or three early wickets we could put pressure on the middle order and that's what happened."
Agarkar's performance not only put his team in control of the match but also helped exorcise some of the ghosts of his last tour of Australia when he bowled reasonably well but was lampooned after making five successive ducks with the bat.
"The ball came out right today. I probably got lucky to get six wickets. It's not everyday that happens," he said.
"They go for their shots, they try and play positive cricket so that gives the bowlers a chance. I felt good from the first ball today and things worked out well for me."
