Team Sky leader Froome crashed before the first of two categorised ascents in the rolling 169km stage from Alhendin to Alcaudete. Despite dropping back for treatment to a series of gashes, the 2013 Tour de France champion shrugged off his fall by surprising the peloton with a kick in the final straight.
Froome's acceleration saw the 29-year-old take two seconds from race leader Alejandro Valverde (Movistar) and the likes of Alberto Contador (Tinkoff-Saxo), Nairo Quintana (Movistar) and Joaquim Rodriguez (Katusha) as the peloton came home 2:20 down on stage winner De Marchi.
Cannondale's De Marchi was part of a four-man break that disintegrated in dramatic fashion just 15km from the finish on a cooler but nevertheless challenging day in southern Spain.
First, Frenchman Hubert Dupont (Ag2R-La Mondiale) was dropped as the road edged up on yet another uncategorised climb; then Canadian Ryder Hesjedal (Garmin-Sharp) lost his front wheel on a slippery corner and skidded out.
De Marchi and Switzerland's Johann Tschopp (IAM Cycling) initially slowed before it became clear that Hesjedal had been held up further after a TV motorbike ran over his Cervelo bike - sent spinning across the road after his tumble. De Marchi then surged clear before soloing to a maiden Grand Tour stage victory.
Hesjedal recovered to take second place on the stage, leading his two fellow escapees over the line 1:35 in arrears.
Belgium's Philippe Gilbert (BMC) responded to a dig by Ireland's Dan Martin (Garmin-Sharp) to dart across the line ahead of the peloton for fifth place at 2:17. Both Martin and Froome crossed in his wake, three seconds ahead of the pack.
A crash in the home straight saw French youngster Warren Barguil (Giant-Shimano) - a double stage winner last year - hit the deck at top speed. Wincing in pain and clearly in shock, Barguil pushed his bike across the line minutes later - but as the incident occurred within the final 3km the 23-year-old retained his ninth place on GC.
Spaniard Valverde leads the race after the opening week with Movistar team-mate and Giro d'Italia winner Quintana 15 seconds behind in second place. Spain's Contador is 18 seconds down in fourth place while Froome is now just one second further back in fourth. Colombian youngster Estaban Chaves (Orica-GreenEdge) completes the top five at 44 seconds.
FOUR-MAN BREAK: A hectic start saw over a dozen riders break clear of the peloton, including Britain's David Millar - riding his final Grand Tour for Garmin-Sharp before retirement.
Millar's team-mate Hesjedal and Tschopp rode clear on the Cat.3 Alto de Illora and were soon joined by De Marchi and Dupont after the remainder of the initial larger group was swallowed up by the pack.
By this point, Froome had already come to grief in a crash involving double stage winner John Degenkolb (Giant-Shimano) and former Italian champion Ivan Santaromita (Orica-GreenEdge). After breaking a finger in the fall, Santaromita was taken to hospital and became the first of the peloton's 198 riders to withdraw from the race.
Tschopp crossed the summit in pole position as the four leaders combined well to build up a maximum lead of seven and a half minutes. With Hesjedal 7:49 down on GC at the start of the stage, the Canadian's GC hopes were seemingly given a lifeline.
Trek Factory Racing and Lampre-Merida combined to lead the chase but it became clear that they had left it too late. Tschopp took the points on the Cat.2 Alto Ahillo and the break was cruising with a lead of well over three minutes on the pack when Dupont slowed and Hesjedal dramatically skidded out.
Once De Marchi shed Tschopp it quickly became clear that he would hold on for the victory. Winner of a stage in last year's Criterium du Dauphine, 28-year-old De Marchi had the luxury of being able to celebrate with his Cannondale directeur sportive before crossing the line.
Having pointed to the sky and then to his sponsor, De Marchi then punched the air as he secured the biggest win of his career with a huge grin on his face. Hesjedal was left to rue his bike handling, his stab at glory reduced to an exercise in trying to retain as much gained time as possible.
His huge efforts saw the Canadian merely rise to 37th place, 7:13 down on the red jersey Valverde.
RIDE OF THE DAY: Renowned for his persistent attacking, De Marchi was finally rewarded for his consistent efforts to win from a break. Elected the most aggressive rider in the Tour de France, the Italian never finished above fifth place in July. We will never know whether De Marchi would have won the stage had Hesjedal not crashed 15km from the finish - but he certainly looked the strongest rider in the break so the win was just deserts, even if it seemed a little anti-climatic given the circumstances.
DAY TO FORGET: Australian veteran Cadel Evans can kiss his GC hopes goodbye after the BMC rider came home more then eight minutes down on De Marchi. Evans, likely to be riding his final Grand Tour, will now have to seek stage wins if he wants to bow out with a bang. Andrew Talansky's horror race continues after the American Garmin rider shipped over 14 minutes while French tyro Barguil will have a sore night's sleep on store after hitting the tarmac on the closing straight.
COMING UP: Saturday's 220km stage eight from Baeza to Albacete could prove a bit of a snore-fest for fans - unless crosswinds on the planes of Castile-La Mancha come into play; in which case, the results could be devastating. Either way, expect a tight bunch sprint with the likes of Nacer Bouhanni (FDJ) and John Degenkolb (Giant-Shimano) chomping at the bit.
- Sports & Recreation
- Johann Tschopp
- Ryder Hesjedal
- Alberto Contador
- Alejandro Valverde