Coentrao, brought on for Marcelo after 70 minutes, appeared to be appealing for a handball by Sporting substitute Joel Campbell when the ball hit his raised arm in the box, and home captain Adrien Silva made no mistake from 12 yards.
Benzema wins it for Los Merengues
However, second-half sub Benzema kept Real in contention to top their group six minutes later when he glanced skipper Sergio Ramos' cross past the despairing dive of goalkeeper Rui Patricio and into the corner.
Real Madrid XI: Navas, Carvajal, Ramos, Varane, Marcelo, Vázquez, Kovacic, Modric, Bale, Isco, Cristiano
20:36 | It looks like Isco has another shot at playing in his best position this evening, then. Perhaps it'll help assuage the (not unjustified) game time-related doubts he reportedly has about renewing his contract at the club...
20:33 | Reports in Italy say Inter Milan have sent a representative tonight to run the rule over Sporting's Gelson Martins and Real's James Rodríguez, who is on the away side's bench and currently tumbling down the Bernabéu pecking order.
20:25 | As the players warm up at the Jose Alvalade, the video screens are showing top moments from throughout Cristiano Ronaldo's career. Meanwhile, the man himself has been speaking to Real Madrid's in-house media of his happiness at returning to his first club - the short interview is certainly worth a shufties.
20:20 | On the subject of Real Madrid's away form in the Champions League (see 20:11): for the sake of balance, it's also worth pointing out that the European champions are unbeaten away from home in the group stages for four years, going back to October 2012.
20:16 | The teams are out for their pre-match warm-up (which at this level never seems to consist of everyone standing around taking shots at goal, disappointingly). As expected, there was a hero's welcome for Mr. Ronaldo.
20:11 | ...And Madrid's recent away form in the Champions League is distinctly patchy: they've not triumphed on the road in Europe's premier club competition since a 2-0 win at Roma in last season's last 16, way back in February. Since then, they've registered three draws (at Manchester City, Borussia Dortmund and Legia Warsaw) and one defeat (at the hands of VfL Wolfsburg).
20:09 | Real may only need a point to qualify tonight, but - unless Legia can spring a surprise at Dortmund - Zidane's men need a win to keep their hopes of topping Group F intact (although there's some debate over whether it'll actually matter which position they go through in)...
20:06 | 40 minutes to kick-off in Portugal - why not have a cheeky perusal of this interview with the man who handed Cristiano Ronaldo his Sporting debut?
20:01 | Sporting boss Jorge Jesús gives his pack a jolly thorough shuffling from Friday's 5-1 cup win over Praeinse: I make it no fewer than nine changes.
19:54 | So, Benzema is on the Real Madrid bench alongside, Casilla, Nacho, James, Coentrao, Asensio and Danilo. Ramos makes his first appearance for Real since way back in late September, when Los Blancos drew away to Borussia Dortmund.
19:50 | As we wait for Jorge Jesús to reveal his line-up to the baying masses, it's worth noting that the hosts may have the slight edge in terms of freshness, having played their weekend Portuguese Cup clash on Friday evening, 24 hours before Real's derby win.
19:48 | Zinedine Zidane has named his XI to play Sporting (see above). Just the one change to the side that beat Atlético, as captain Sergio Ramos returns to fitness and comes in for Nacho Fernández at the heart of the defence. It looks like we'll see a reprisal of the (from right to left) Vázquez-Modric-Kovacic-Bale midfield, with Isco tucked in behind Ronnie (or Modric and Kovacic behind a Vázquez,Isco and Bale, depending on which way you look at it). No word from Sporting yet, the rotters.
19:30 | We'll be bringing you all the team news as it comes in over the next half hour or so. For the hosts, only forward Lukas Spalvis is out injured. As for the visitors, the chief question marks surround the return of Sergio Ramos and Karim Benzema to the line-up, and whether Zidane will maintain Saturday's 4-4-2/4-4-1-1/4-2-3-1/'Disco Isco Formation'. If Benzema comes back into the XI - which, one imagines, would be at the expense of the always excellent Lucas Vázquez - then the smart money would be on a good ol' 4-3-3 with the 'BBC' up top.
19:25 | One man to watch in green and white tonight is young Portugal international Gelson Martins, who's thought to be interesting this evening's visitors - and a whole host of other cheque-book wielders. He is fit and in line to play tonight despite a little prang-ette at the wheel of his snazzy sports car the other day.
19:19 | Real Madrid visited Sporting in the Champions League in the 2000/01 season and were held to a 2-2 draw, while Los Merengues also failed to come away victorious from Lisbon in the 1994/95 UEFA Cup, going down 2-1 (though they did win that first-round tie on away goals).
19:13 | 'CR7' goes into this evening's Sporting reunion just two shy of becoming the first player to chalk up 100 goals in European competition. So far, the man from Madeira has 95 in the Champions League proper, one in Champions League qualifying and two in the UEFA Super Cup.
18:36 | With just under two hours to go until Willie Collum delivers a short, sharp peep on his shiny whistle, here's another reminder of how and where to watch.
18:26 |Cristiano returns to the Jose Alvalade to face Sporting for the second time in a competitive fixture, having also gone back with Manchester United in the Champions League in September 2007. That night he got the only goal, and in three games in total against his first club - all in Europe's elite competition - he has always found the net.
09:12 | Good morning and welcome to our build up and live coverage as the Champions League returns.
Sporting Lisbon - Real Madrid: match preview
The Champions League is back after a short break and with only two games remaining teams that have not yet done so are hoping to clinch qualification with a game to spare. For Sporting this is more of a pipe-dream as they know even a draw tonight would eliminate them from the competition. If that was to happen, Madrid would ensure a place in the knock-out rounds. One thing is for sure, it's going to be a bit of a love-in for one man as the José Alvalade stadium welcomes home their prodigal son.
Jorge Jesús comes into this match knowing that anything but victory will end his team's Champions League participation for another year but also on the back of a convincing 5-1 Portuguese Cup win. Confidence can also be taken from the last meeting between these two sides where a very late Morata goal nicked all three points for Madrid at the Bernabéu.
With the emotive home support Sporting can again be competitive and in Gelson Martins they have a young lad that is capable of shining. Indeed, reports suggest that scouts from around the globe will be in attendance tonight to see the 21-year old against a more challenging opponent than he faces from week to week. Jesús has already compared him to Luis Figo.
Other decisions to be made include whether to bring back Sergio Ramos at the heart of defence - this will be determined purely by fitness levels - and how to accomodate Isco, who was a star attraction in a supporting front role against Atlético. If Benzema does indeed start in a front three then Isco will be forced to adapt as part of a three behind - ahead of Modric and Kovacic. But after Saturday's result, Zidane may be open to new formations.
Coach: Jorge Jesús
Coach: Zinedine Zidane
Sporting Lisbon - Real Madrid: live match build up