Charlton were left one point above the drop zone after their latest defeat at The Valley, 0-1 to Bolton Wanderers.
Nathan Jones made six changes from the side which lost 3-0
at Middlesbrough on Saturday, with goalkeeper Arthur Okonkwo among those left
out.
Chalobah was making his first start since he was injured in
the win over Preston on 29 August, which was the last time Charlton picked up
three points, but he had an inauspicious return.
With little threat on halfway, he played an aimless ball
back towards his own goal and Dalby had enough pace to escape the defence
before expertly planting his shot past Will Mannion in goal.
The midfielder was taken off at half-time, but the damage
was done as Charlton huffed and puffed in their attempts to get back in the
game, after Danny McNamara and Harvey Knibbs had come closest to scoring for
them in the first half.
Bolton sat back after the break as Charlie Kelman's header
and Conor Coventry's flashing shot were both inches away from levelling, but
full debutant Max Lott almost doubled the lead as Bolton menaced on the
counter.
The visitors had a tricky moment to survive when goalkeeper
Jack Bonham inexplicably picked up Josh Sheehan's back pass, giving the home
side an indirect free-kick on the edge of the six-yard box.
Knibbs went for power and Sheehan injured an ankle by
bravely hurling himself in front of it, and was forced off a few minutes later,
but he had done his job, although Tyreece Campbell curled a shot narrowly side
in added time.
Stunned supremo Nathan Jones said: "In terms of
endeavour, in terms of work-rate, in terms of passing the football there was
zero problem. We've had more possession, more touches in the opposition box,
and so many opportunities in and around their box, but we've gifted them a goal
- they haven't had to work for it in any way.
"We had no problem all night and then gifted them a
goal. Then we just didn't demonstrate enough quality in the final third, with
the amount of opportunities we've had to cross it, to put it in areas, corners
and free kicks.
"It wasn't any individual. We've probably made more
positive substitutions tonight than is humanly possible, but we just didn't
demonstrate enough quality. We aren't doing the out-of-possession stuff well
enough because we are gifting goals."