's face was a picture as several of his team-mates declined to join him in celebrating Arsenal's second goal on Thursday night. In truth, he shouldn't have been so surprised.
If he didn't know about their feelings towards him before, he would have got the gist during a dressing-room inquest after Arsenal scraped a 1-1 draw at Southampton earlier this month.
Sanchez wasn't at his best at St Mary's — a common theme so far this season. After the final whistle, a group of players made their feelings clear.
During the game Jack Wilshere, who came through Arsenal's academy, is said to have confronted Sanchez about his wastefulness in possession.
Sanchez's popularity at Arsenal's London Colney HQ has plummeted in recent months, and some members of the Arsenal squad — and even backroom staff — have had enough of the Chilean.
There are some who want him out next month, others who wish he had been sold last summer.
Dressing-room divisions are not new. Teddy Sheringham and Andy Cole fell out at Manchester United, yet still won major trophies together.
Less well known is that Aaron Ramsey and Robin van Persie didn't always see eye-to-eye during their time together at Arsenal. Their mutual dislike was kept under wraps by Arsene Wenger.
When players cross the white line on matchday they put on a united front. That's what Sanchez expected when he scored twice to help the Gunners win 3-2 at Selhurst Park on Thursday night.
The fact a number of his team-mates left him hanging speaks volumes. The snub was not planned but it was meaningful. Wenger did his best to brush the problem under the carpet after the game.
'I didn't see that,' he said. Indeed, Wenger could well demand a show of unity if Sanchez scores when Arsenal go to West Bromwich on Sunday.
If that happens, it will be through gritted teeth.