Cheltenham boss was relieved to end up on the right side of a ‘hairy scary’ finish after his team edged out Exeter 1-0.
The Robins took a big step towards promotion from Sky Bet League Two, with substitute Andy Williams bundling home the only goal of a tight contest in stoppage time.
It was a harsh defeat on Exeter, who had created the better of the very few chances throughout the game, but the one time they failed to deal with a long Ben Tozer throw proved costly.
Exeter failed to clear their lines and as the ball bobbled around the goalmouth, Williams bundled it over the line from close range to keep the Robins at the summit.
Duff said: “I am delighted. It was a really close game between two good teams in difficult conditions.
“Chances were at a premium. I thought we played well in the first half without testing their keeper. We started the second half brightly, and it gets a bit hairy scary at the end.
“The pleasing thing is that Exeter are the top goalscorers in the league by a long way and to keep a clean sheet is really pleasing.
“Our keeper (Josh Griffiths) has made a good save when their lad went through. If they had scored that, they would have probably won 1-0.
“Exeter are a proper promotion-chasing team and I expect them to be up there. They have got some good players and they can mix it up.
“Ryan Bowman is a good player and I told the back three if they don’t look after him you don’t win the game. I am really pleased with every aspect of the game today.”
The two teams had shared eight goals earlier in the season, with Cheltenham winning 5-3, but there was no sign of a repeat in a first half devoid of anything clear-cut.
After the break, Exeter were the better team and twice had chances to go on front, but captain Jake Taylor spurned both, blasting them both over the crossbar.
Substitute Robbie Willmott had perhaps Exeter’s best opportunity when he was played through on goal, but he shot straight at Lewis Freestone.
It took until the 84th minute for Cheltenham to create anything of note, but Alfie May was denied by a brilliant save by Exeter goalkeeper Jokull Andresson.
However, Andresson could have done better for the goal as his indecision led to a panicked Exeter clearance and a throw-in for the Robins. Tozer’s long throw is well known and Exeter were unable to clear their lines, with Williams prodding home from close range.
Exeter manager Matt Taylor was disappointed that his side conceded so late in the day, but felt they had not done enough to win the game either.
“I see it as one point dropped rather than missing out on three,” he said.
“It’s a tough way to lose the game, but there was nothing in it. They are a top team but we showed we can more than match them and we probably had the clearer chances throughout the game.
“I am disappointed that it has come down to that one moment in the 91st minute because it was a game where neither team could implement their quality players and the ironic thing is that I said on Thursday you want the quality players to be on the pitch.
“It suggests that our defence was on top and their defence was on top, but we didn’t quite capitalise on the moments we had the ball further away from their goal.
“There were too many mis-controlled balls in the middle of the park and they didn’t quite break for our more dynamic players.
“We improved towards the end of the game – and as the game went on – and Robbie Willmott’s introduction helped that, but it looked like it would be a 0-0 until one long throw.
“We didn’t quite meet that first ball and it is the only time we didn’t.”