Athletic could have had a penalty when Inaki Williams was pushed by Dani Carvajal as he shaped to shoot, before the visitors were reduced to 10 men when Raul Garcia was sent off for two quickfire fouls on Toni Kroos. Vinicius Junior had the best chance of the half when his close-range effort was saved by keeper Unai Simon and then Kroos gave Madrid the lead right on half-time, shooting low into the bottom corner.
Athletic threatened a surprise after the break when Ander Capa equalised. A Madrid rally followed as Vinicius had an effort ruled out for offside, a handball penalty appeal was denied and Benzema headed Carvajal's cross past Simon with 15 minutes left before scoring again in the last seconds of the game after Thibaut Courtois had saved from Mikel Vesga at the other end.
This was a potentially tricky fixture for Real Madrid, when the team could easily have lost their focus and slipped up after three significant wins in a row. The lack of a suspended Casemiro was another warning sign. Instead, Garcia's needless early sending off, a midfield masterclass from Kroos and some clinical finishing from Benzema made sure that Athletic's 15-year winless streak at Real was maintained.
The team are so reliant on Benzema's goal scoring and his form is hugely encouraging, along with that of Kroos and Carvajal too, since his return from injury. The right-back's contributions in attack should not be underestimated.
This was a largely businesslike, even workmanlike performance, and there were spells in the second half when Madrid struggled more than they should have against 10 men, although perhaps that's understandable given the fixture list. There have been frequent, and justified, complaints from coach and players about the hectic schedule, and squad players will need to step up and play their part over the course of the season.
Zinedine Zidane's ditching of his preferred, much-discussed rotation policy may only be temporary -- and could be restored as soon as this coming weekend -- but his recent reliance on tried-and-tested veterans like Luka Modric, Kroos and Benzema could prove costly later in terms of tiredness or, worse, injuries.
Manager rating out of 10
7 -- Zidane's starting XI was a surprise. The coach seemingly didn't want to risk changing a winning team, with only Federico Valverde returning from a shin bone fracture to replace Casemiro. The decision was the right one, treating the match with the seriousness it deserved, although the coach won't have been happy with Madrid's second-half wobble. Substitutes Isco, Marco Asensio and Rodrygo were all logical introductions given the state of the game.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
GK Thibaut Courtois, 7 -- No first-half saves to make. Kept Capa's first effort out, and was left on the floor as he dispatched the second. A huge, game-changing added-time stop to deny Vesga.
DF Dani Carvajal, 8 -- Could have given away a penalty with an early shove to put Williams off balance. Tracked back well to cut out a dangerous ball into the box before half-time. Crossed expertly for Benzema's winner.
DF Raphael Varane, 6 -- Has started more games than any other outfield player this season and could do with a break.
DF Sergio Ramos, 6 -- Left Capa in space for Athletic's equaliser when he went chasing the ball instead, a regular defensive failing of his.
DF Ferland Mendy, 7 -- Didn't catch the eye like Carvajal, but didn't play badly either. A very, very optimistic shot with his wrong foot in the second half.
MF Federico Valverde, 6 -- Back after five weeks out and will take time to get back to his best. Only ready to play 60 minutes at this stage. Shot wide twice in the first half.
MF Toni Kroos, 8 -- Caught twice early on by Athletic bruiser Raul Garcia as he was sent off. One tentative first-half shot was followed by a much better, pinpoint effort from distance for his 20th Real Madrid goal.
MF Luka Modric, 7 -- His fourth start in 10 days, at the age of 35. A quieter display this time, which perhaps suggested a rest is overdue. An assist for Benzema in added time.
FW Vinicius Junior, 7 -- Dived looking for a first-half penalty. Put Madrid's clearest chance of the half into the body of Simon and had a second-half effort ruled out. Taken off after an hour, it's now almost two months without a goal.
FW Lucas Vazquez, 6 -- Has now started nine games in a row but may come out of the team now. Yellow carded before half-time for a bad challenge on winger Alex Berenguer.
FW Karim Benzema, 9 -- One outrageous early piece of skill, controlling the ball with his back, was followed by another later in the first half when he danced past two defenders to find space inside the box. Scored his third header in a row, and then grabbed a late goal to secure the three points.
MF Isco, 6 -- Introduced with half an hour to go after being an unused sub in all three games last week. Zidane says he's to blame for not giving the playmaker chances but this was another opportunity to impress that Isco failed to take.
FW Marco Asensio, 6 -- Took the short corner that led to Benzema's goal but can't take too much credit for that. One late curling shot wide.
FW Rodrygo, N/R -- Played the last 20 minutes.