The 29-year-old missed the Gunners' crucial 1-0 win over Burnley at Turf Moor on Sunday afternoon through illness.
Arsenal skipper Laurent Koscielny struck a controversial victor in time added on in the corresponding fixture last season and Sanchez's late spot-kick sank Sean Dyche's side at the Emirates in January this year.
But just when it appeared Burnley had taken another point off one of the Premier League's top six - they won at Chelsea on the opening day and have drawn against Liverpool and Tottenham - Tarkowski's push was spotted by referee Lee Mason and Sanchez condemned them to their third league defeat of the season.
"We changed a bit of shape (at half time), I felt we had to give more".
Arsenal manager Arsene Wenger: "It looked from the outside like a clear penalty". "It's a tough one, it probably is a penalty, but my point is it was never not going to be given on today's performance, I can assure you". But at that stage of the game, you have to be 100%, which I presume the referee was.
"I've got this as a draw again". It pointed to how Arsenal were edging the half but had to stay alert.
Wenger has come under fire at The Emirates in recent seasons after failing to guide Arsenal to the Premier League title since their famous unbeaten triumph in the 2003-04 campaign. They have now conceded 10 times in their 13 outings this season, leaving the high-flying Manchester rivals as the only teams in the division to keep the goals against column in single figures. Two minutes too many for them, as it transpired. They had shaded the first half and defended stoutly throughout the second. This time some Gudmundsson trickery bought a yard and he crossed towards the lurking Ashley Barnes.
The Arsenal boss has made a decision to replace Ozil with Alex Iwobi who will start alongside Lacazette and Sanchez as part of the Gunners attacking trio. Subs: Jack Wilshere (for Iwobi, 67) 6, Danny Welbeck (for Lacazette, 79) 5.