Nicolau opened the scoring for the second successive game when he saw his 26th minute free-kick from the right float over a packed area and into the net but once again a lack of a second goal proved crucial as, after both Alan Power and Andrew Boyce were forced off injured, Alfreton bounced back.
Striker Anthony Wilson levelled in the 64th minute following a quick attack after substitute Jake Sheridan appeared to be fouled in the Imps' attacking third whilst the killer blow came with 10 minutes on the clock when skipper Darran Kempson headed past Paul Farman after the City defence failed to deal with a free-kick into the box.
There were two changes to the starting line-up for this Blue Square Bet Premier game against Alfreton Town at The 12th Imp Sincil Bank Stadium with Gary Mills, who limped off against Ebbsfleet United on Saturday, and Jake Sheridan dropping to the bench. In their place came Paul Robson and Peter Bore; the former slotting in at right-back with Dan Gray moving into midfield whilst the latter was in on the right for his first appearance of the season.
Alfreton, with five changes to their starting XI, kicked off and it was a fast and furious opening to proceedings with the Imps enjoying the better of the early exchanges, although visiting 'keeper Jon Stewart was untroubled in a goalless first five minutes.
Town's response was to win the first corner of the game but this was easily dealt with by the City defence and shortly afterwards, Paul Farman was well positioned to claim a 20-yard Dan Bradley drive.
City's first real attack of note came in the 12th minute when a quick break forward by Jamie Taylor saw him spot a gap in the Town back-line but, after he slotted a pass through Bore drilled over rather than in from just inside the box.
Bore was in the action at the other end four minutes later, being forced to concede a corner but it wasn't long before the game entered a scrappy period with chances at a premium. That all changed, however, in the 26th minute when Nicky Nicolau bagged his second in as many games.
Nicolau, who opened the scoring against Ebbsfleet at the weekend, repeated the feat direct from a free-kick, given after Theo Streete had gone in late on Colin Larkin, with his delivery from the right flank going over a packed box with Andrew Boyce happy to watch the ball hit the back of the net as he ghosted in at the back post.
A knock to Alan Power seconds after the restart brought about a break in play before the midfielder was attended to off the pitch by physio Sam Rees. It soon became clear that Power was unable to resume his duties with a far-from-fit Gary Mills coming on in his place. Power made his way to the dressing rooms on a stretcher, adding to manager David Holdsworth's injury woes.
City had Paul Farman to thank when play resumed, with the stopper superbly tipping away a goal-bound Nathan Arnold drive and when the ball was played back in, Daniel Meadows went in hard on the Imps' number one, leaving him winded on the deck.
A minute before the break a foul on Taylor gave Nicolau another chance from a dead-ball situation but this time his low effort crashed against a visiting defender before the ball was hacked away.
The half ended after a couple of minutes' additional play.
HT: Imps 1 Alfreton 0
City restarted play and were quickly pushing forward with Nicolau firing a dipping right-footed volley a couple of feet over from 25 yards. A minute or so later, Andrew Boyce was left grounded after being on the end of a heavy Anthony Wilson challenge.
A cynical challenge on Taylor by Streete then earned the Town defender a yellow card with Taylor's flicked header from Mills' resultant free-kick being hurriedly cleared by the visiting defence.
Boyce was on the floor again a minute later and for a second time a stretcher crew was called into action, only for the big defender to get to his feet before being helped off by physio Sam Rees and nurse Bev Gambles. Jake Sheridan came on as his replacement with Gray dropping back into central defence.
Two minutes after this latest injury blow, good pressure from Larkin saw him force a mistake from the Town defence. The ball ran to Taylor who advanced but, with Mills up in support, the striker went alone before drilling wide of the target.
Larkin was then left clutching his head after an aerial challenge by Leigh Franks, who picked up a deserved caution for his troubles. A fizzing low centre from Nutter then flew across the box as the Imps continued to press for a second.
The second of the game did come in the 69th minute but unfortunately it was the visitors who bagged it. With Sheridan grounded on the right after being tripped only for nothing to be given, Alfreton broke at pace and after Arnold had an effort blocked the ball ran for Anthony Wilson who fired a shot on the turn past Farman to draw his side level.
Before play restarted Sheridan was cautioned for airing his frustrations to vociferously for referee Chris Knowles' liking and when it did resume, a Meadows cross-cum-shot was palmed away from under his bar by Farman.
With Alfreton suddenly brought to life following their equaliser, Arnold rattled the post with a downward header following a cross into the area and when the ball ran loose, Connor Franklin sliced well wide.
A long Franks throw was then looped over his own bar by Larkin and when the deep corner was played in, skipper Darran Kempson headed a foot wide. City's response saw Taylor have a low show blocke by Stewart and when Larkin latched on to the loose ball, his effort tricked agonisingly goalwards but with no team mate up in support, the Town defence were able to deal with the danger.
In the 76th minute Paul Clayton for Anthony Wilson up front was Alfreton's first change and he was quickly in the action going up for a number of headers as the visitors pumped the ball high towards the edge of the City box.
The visitors kept up the pressure and when a free-kick was played in to the area, Bradley helped the ball on and there to beat the advancing Farman to the ball was captain Darran Kempson whose header had enough power on it to find the back of the net.
City had 10 minutes left in which to salvage something from the game but they were almost 3-1 down when Anton Brown saw his goalbound header tipped over by Farman.
In a last throw of the dice, Vadaine Oliver came on for Paul Robson and seconds after this switch a Sheridan ball saw Taylor bear down on Stewart only for his effort to deflect behind. The Town 'keeper remained grounded, before hobbling back to his feet after treatment. When play resumed he palmed away a Taylor header from the corner before smothering the loose ball.
The Fourth Official indicated that a minimum of six minutes were to be added on but Alfreton continued to hold firm with nothing going for the Imps in the attacking third. More time elapsed when goalkeeper Stewart was booked for kicking the ball away as the Imps prepared to take a throw-in.
In the last of the six extra minutes, Farman went up for a long Gray throw-in only for referee Knowles to award a goal-kick despite the ball clearly coming off a blue shirted player. Appeals for a corner were duly waved away and when Stewart poumped the ball forward from the six-yard line, the official brought play to a close.
FT: Imps 1 Alfreton 2
City: Paul Farman, Paul Robson, Andrew Boyce, Graham Hutchison, John Nutter, Dan Gray, Alan Power, Nicky Nicolau, Peter Bore, Colin Larkin, Jamie Taylor.
subs: Gary Mills (for Power 31), Jake Sheridan (for Boyce 55), Vadaine Oliver (for Robson 83), Conner Robinson, Jake Turner.
goals: Nicolau (26)
bookings: Sheridan (65)
Alfreton: Jon Stewart, Josh Law, Connor Franklin, Darran Kempson, Leigh Franks, Daniel Meadows, Theo Streete, Dan Bradley, Anton Brown, Anthony Wilson, Nathan Arnold.
subs: Alistair Taylor, Paul Clayton (for Wilson 76), Simon Russell, Ashley Worsfold, Ben Tomlinson.
goals: Wilson (64), Kempson (80)
bookings: Streete (50), Franks (59), Stewart (90+3)
Referee: Chris Knowles
Assistants: Andy Aylott & Stuart Richardson
Fourth Official: Sean Feerick
Attendance: 1,566 (96 visiting supporters)