The Magpies drew 3-3 with Gary Waddock's Aldershot Town in a thrilling contest - watch match highlights here.
Aldershot led twice after goals from Jim Kellermann and Adam McDonnell but Adrian Clifton and Dean Inman each levelled things up.
Four minutes from time Harry Pritchard netted a penalty which looked to be handing Maidenhead the points until Kellermann had the final say late on.
"We defended poorly," Devonshire told the Maidenhead Advertiser. "That's why I made the change at half-time and I felt that in the second half we dominated. Once we got 3-2 up I couldn't see them scoring.
"The ball ricocheted and fell for him (Kellermann) on the edge of the box.
"We should have done better but I'm not going to lay into them. We've got a 3-3 draw against a good side and maybe could have won it."
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