Tottenham will clinch fourth spot in the Premier League with victory at City while a draw would also leave the north Londoners favourites to crack the top four but the sight of Brazilian Heurelho Gomes hobbling after Saturday's 1-0 defeat of Bolton Wanderers could throw a spanner in the works.
Gomes, unrecognisable from the error-prone keeper of early last season, has been a formidable last line of defence for Tottenham in their pursuit of Champions League qualification but suffered a worrying 90th-minute groin injury against Bolton.
Should he fail to recover it would mean Alnwick, who signed from Sunderland in 2007, but has managed just two brief appearances as substitute, would be thrust into the heat of the club's biggest game since the climax to the 2005-06 season when defeat at West Ham United cost them fourth place to Arsenal.
While manager Harry Redknapp is calm about the prospect of Alnwick facing the City firepower of Carlos Tevez, Emmanuel Adebayor and Craig Bellamy, it is bad timing for Spurs who will be praying that skipper Ledley King's knee holds up for game they dare not lose.
At least Hungarian Fulop, who was cast off by Tottenham in 2007 before ending up at Sunderland, will have the benefit of a recent taste of battle after playing in City's vital 3-1 victory over Aston Villa on Saturday.
A controversial emergency loan signing by City boss Roberto Mancini last week after regular keeper Shay Given dislocated his shoulder, Fulop looked nervous between the posts on Saturday but is still a more experienced keeper than Alnwick who since joining Spurs has drifted out on loan at Luton Town, Leicester City, Carlisle United and Norwich City.
"I don't want to be a hero, I just want to do a job for the club. That's why I came here, I want the team to be the heroes and then we can celebrate at the end of the season," Fulop, who was given the green light to join City by the Premier League last week, told the club's website.
"You're always trying to prove yourself, and at this level you can never take your foot off the gas. But I don't consider this situation like I'm in a shop window, what's most important is for City to be in the Champions League next season."
Tottenham have not got caught up in the rights or wrongs of City's plea to sign Fulop despite having Faroe Islands international Gunnar Nielsen in reserve, although Redknapp could not resist a sly dig at the decision.
"We're going to get on to the Premier League and see if we can get another two keepers in," Redknapp joked after Saturday's win which kept Tottenham one point above City in fourth spot with two games left. But seriously, we're fine. Ben's a good keeper - I'm fine with him."
Gomes was due to have a scan and will be given every chance to recover for a game that for the winner could unlock the door to the riches of the Champions League and, just as importantly, the prestige and profile both ambitious clubs crave.
"It's a big game, probably the biggest club game I've played because the Champions League is at stake," Tottenham's midfield playmaker Luca Modric told the club's website.
