Saturday's 3-1 victory over Burnley may have not been the most convincing but it was crucial for Liverpool.
As Manchester City had done against Everton earlier in the day, the Reds managed to secure all three points despite playing well below their best, ensuring they maintained their spot at the top of the table for the time being.
Trent Alexander-Arnold was also withdrawn at half-time after suffering a recurrence of the knee injury that kept him out earlier this season, but Liverpool were able to edge their way to victory regardless.
The last and only other time it has occurred in the Premier League came back in 2003, the Reds beating Bolton Wanderers 3-1 thanks to headers from Sami Hyypia, Florent Sinama Pongolle and Vladimir Smicer.
Burnley also netted with a header in the first half through centre-back Dara O'Shea, with Reid also stating that it was the first game which contained four or more goals that were all headed in the Premier League since 2015 in a match between the Clarets and West Bromwich Albion.
Nunez's was the pick of the headers on Saturday for Liverpool, the Uruguayan deftly redirecting Harvey Elliott's cross at the far post.
Diaz also powered home from an Elliott delivery shortly after half-time after Jota had nodded Liverpool in front from Alexander-Arnold's corner after half-an-hour.
According to Transfermarkt, Liverpool doubled their tally of headed goals in the Premier League against Burnley, their total now standing at six from 55 goals for the campaign.
Liverpool's title rivals Arsenal currently lead the way in the English top flight, with 13 of their 53 strikes being headers.