The home side took the lead early through Dean Bowditch, but Jordan Rhodes rose with a header to salvage a point for the away side in the dying embers of the game.
Boro dominated possession and threatened throughout and despite admitting the feeling of frustration, Leadbitter was satisfied with how his team never gave in on the night.
“We’re frustrated (not to win) but we came away with a point – an away point, so we’re pleased,” said the Boro captain.
“It shows the spirit within the lads because I think we dominated the match in the second half. We kept passing and stayed together then got our reward in the end.
“Yes we wanted to win the game but it’s a point away from home and we’re top of the league.”
Karl Robinson’s side tested the Teessiders’ patience, sitting back and inviting pressure after going in front.
But Boro were methodical and persistent going forward, and left with a point after the header from Rhodes which turned out to be one of the final touches of the game.
“We have to do better,” said Leadbitter. “A lot of teams are going to sit back and do that now like last season.
“But at the end of the day we’ve come away with a point and we’ll move on.
“We have to be patient but we want and have to do more to get back to winning ways.
“The last two draws could be big draws at the end of the season so we’ll take that into next Monday night.”