Their task was made all the more difficult by the absence of 11 first-teamers, but they did not wilt under the pressure and Tim Sherwood's side secured a morale-boosting 2-2 draw in a fascinating end to the match.
The manner of performance and display will have pleased the under-fire boss, especially given the fact Spurs' uphill struggle became even steeper when Ezequiel Garay powered home a first-half header.
It looked to have effectively ended the tie in which there were no repeat of the fireworks between Sherwood and Benfica counterpart Jorge Jesus, only for summer signing Chadli to turn the match on its head.
The Belgium forward netted a quickfire brace which was followed up by Aaron Lennon, Gylfi Sigurdsson and Harry Kane efforts, as well as a strong penalty claim before Lima tucked away a spot-kick for the hosts in stoppage-time.
It was an impressive display given the paucity of options at Spurs' disposal, highlighted by the fact seven of the 21 players that travelled to Portugal had not yet played for the first team.
Five of them - Jordan Archer, Milos Veljkovic, Connor Ogilvie, Dominic Ball and Harry Winks - were included on the bench at the Estadio da Luz - a "lion's den" Sherwood did not want to throw them into if avoidable.
The main concern, though, was the lack of a recognised centre-back in the side, meaning left-back Zeki Fryers and defensive midfielder Sandro became a makeshift pairing.
Unsurprisingly Benfica attempted to get at their defence from the outset and, like in the first leg, they looked susceptible from set-pieces.
Luisao netted a brace from dead balls in the first leg and should have put another past Spurs with the hosts' first corner, only to direct his header wide in the ninth minute.
Tottenham, though, were also threatening and had a fine chance of their own with 14 minutes on the clock when a corner was flicked onto the unmarked Roberto Soldado, who controlled well only to hit a strike into the ground and wide.
The Spaniard was soon back in action again as Spurs pushed for an opener, although a last-ditch block meant he was unable to convert Chadli's cut-back.
The resulting corner saw Chadli header tamely wide as Sherwood's men continued an impressive start in which there were surprisingly few hairy moments at the back.
Benfica, though, went ahead on the night in the 34th minute as Eduardo Salvio saw off Lennon and clipped in a fine ball for Garay to powerfully header home.
Spurs now needed three goals to take the match to extra-time, although that was not enough to quieten the 3,000 travelling fans.
They continued in fine voice as the match entered the second half, which saw Sigurdsson come close to latching onto a neat Andros Townsend ball from the left.
The England winger was enjoying his duel with Maxi Pereira - someone he may again come up against at the World Cup in the match with Uruguay - and soon impressively cut past him again, only for his fierce strike to hit the side-netting after a slight deflection.
A wonderful Sandro tackle on Ruben Amorim thwarted the Benfica midfielder when the hosts returned to the attack before Guilherme Siqueira missed the goal marshalled by Brad Friedel, whose appearance saw him extend his record as the Europa League's oldest participant.
Kane was brought on in a bid to grab a leveller and started a move that resulted in Chadli firing at Oblak, who the Belgium international did beat with 12 minutes remaining as he cut in from the left and lashed home a 20-yard drive.
Benfica fans continued to cheer despite the goal, although that changed when Spurs netted a quickfire second.
Kane knocked a back-post cross into the path of Chadli, who impressively turned to fire a left-footed half-volley into the far corner.
It was a remarkable turnaround and one which would have improved further was it not for Luisao denying Lennon the opportunity to roll into an empty net.
Tottenham continued to press after Salvio forced Friedel into a save, with Kane having penalty claims rejected after being upended in the box by Miralem Sulejmani.
Oblak made fine saves to deny Sigurdsson and Kane as the visitors continued to press, only to get caught by a stoppage-time sucker-punch as Lima netted after being brought to the deck by Sandro.
Source : PA
Source: PA