The Robins fell behind twice in the 2-2 draw, despite having created several chances to win the game.
It means they’re four games unbeaten going into a tough FA Cup first qualifying round tie at Halesowen Town on Saturday, but Carruthers felt it should have been four wins in a row.
He said: “We’re bitterly disappointed. We told the lads at half-time that if we played to our normal strengths we’d win and we knew that their main strengths were from set pieces and the long throw as they’re good at what they do.
“We conceded from a throw in the first-half but then it looked like there would only be one team who would win it in the second-half as they sat back and we missed chance after chance in the last 20 minutes.
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"Then we concede a penalty from a counter-attack and it was poor defending again, and even though we’ve got a point thanks to Zak Goodson’s great finish, we feel like we’ve dropped two points.”
Belper had led through Danny South’s opener on ten minutes but new signing Paddy Webb netted his first Robins goal just before half-time to level the scores.
The Robins saw two efforts cleared off the line and several good openings wasted before Mitchell Tait’s foul on Brodie Litchfield handed Belper a penalty with nine minutes left which Jonny Margetts converted.
However, sub Zak Goodson curled a 25-yarder into the top corner to level things with four minutes to go.
Ilkeston now prepare to visit in-form Halesowen Town in the FA Cup first qualifying round on Saturday, ahead of another visit to the Birmingham area on Monday in the shape of Coleshill Town, subject to any necessary FA Cup replays.
Carruthers said: “We’ve got a tough weekend ahead again but have to defend better as a team, especially at set pieces which we’ll work on.
"Halesowen is a game we want to go and try and win and keep our momentum going and the unbeaten run going too. We might give one or two lads a run out to freshen things up a bit with an eye on Coleshill but we go there to try and win.”