A stoppage-time equaliser spared the Baggies a humbling exit; denying their National League opponents both a shock win and a guaranteed fourth-round tie against either Bristol City or Swansea.
Match preview
Only Brandon Thomas-Asante's last-gasp header prevented West Brom from losing a game in which the Baggies striker had actually put his side ahead within the first two minutes, as a minor FA Cup classic played out at the Technique Stadium.
The visitors' constant pressure finally told, as their late recovery continued a bright start to life under new boss Carlos Corberan, who has overseen nine wins from 12 matches since taking charge in the Black Country.
The former Huddersfield Town manager may have avoided the harshest possible punishment for making 11 changes from his team's 1-0 win against Reading, but West Brom are now obliged to welcome Chesterfield to The Hawthorns in for a midweek replay.
However, they do so from inside the Championship's top six, having beaten Luton Town 3-2 by virtue of an even more stirring fightback at the weekend: from going two down after 10 minutes, they struck back through Daryl Dike, Jayson Molumby and Connor Townsend, to finally break into the playoff places.
Ahead of a daunting visit to second-tier pacesetters Burnley on Friday, West Brom - five-time winners of the trophy - will be intent on avoiding their third straight exit from the FA Cup at this stage.
For all the plaudits that came their way after holding West Brom on home soil, Chesterfield could justifiably feel aggrieved about Albion's late equaliser, as goalscorer Thomas-Asante has since received a violent conduct charge by the FA after a review noted his use of an elbow on Jeff King just before the striker's decisive intervention.
Cheered on by a crowd of almost 10,000 fans, the Spireites had won 15 of 23 league matches before tackling the Championship promotion contenders, but since the dramatic events in Derbyshire they have seen such momentum quelled - their subsequent fixture at Wealdstone was called off due to a waterlogged pitch.
Paul Cook's men, who defeated League Two clubs Northampton Town and AFC Wimbledon to reach the third round, have also won each of their last six home games in the National League, where they sit fourth ahead of this weekend's clash with leaders Notts County.
However, they must now make their way to the West Midlands in search of a first fourth-round berth since 2015, and Cook will have to weigh up his club's priorities given the game's proximity to such a crucial league contest.
Returning to the EFL is surely the ultimate dream this year, but on the evidence of their first encounter with West Brom, Chesterfield cannot be discounted from continuing their run in the cup.
West Bromwich Albion FA Cup form:
D
West Bromwich Albion form (all competitions):
L
W
W
W
D
W
Chesterfield FA Cup form:
W
W
D
Chesterfield form (all competitions):
W
L
W
W
W
D
Team News
Carlos Corberan has something of a striker dilemma to resolve on Tuesday, as top scorer Brandon Thomas-Asante's retrospective three-match ban rules West Brom's top scorer out, while Daryl Dike would ideally be rested after leading the line against Luton and with a trip to Burnley to come on Friday night.
As Karlan Grant and Kenneth Zohore are both injured, rookie forwards Jovan Malcolm and Reyes Cleary could even be involved as Corberan rotates his team again, though midfielders Matty Phillips or Tom Rogic may be pressed into service up front instead.
Reserve goalkeeper David Button is likely to be among numerous changes for the home side, with academy graduate Taylor Gardner-Hickman also in contention to start.
Meanwhile, Paul Cook may be more inclined to field something resembling his strongest XI at The Hawthorns, as his squad have not been in competitive action for over a week and do not face Notts County until Saturday evening.
Therefore, Armando Dobra - who has racked up five FA Cup goals this season following his brace in the first game - should support Joe Quigley in attack. Kabongo Tshimanga, however, will be hoping to get the nod ahead of Quigley based on a tally of seven goals from 17 National League games this term.
West Bromwich Albion possible starting lineup:
Button; Gardner-Hickman, Kelly, Ajayi, Ashworth; Molumby, Ajayi, Livermore; Diangana, Phillips, Reach
Chesterfield possible starting lineup:
Fitzsimons; King, Grimes, Williams, Clements; Jones; Mandeville, Akinola, Oldaker, Dobra; Tshimanga