Quite a long one, so almost certainly something that needs correcting or making clearer. Comments below please:

Qualifying rounds- Matches that you have to play to get into a championship, for example playing other teams in your region for a chance to go to the WORLD CUP FINALS.
Quarter finals- The stage before the SEMI FINALS, where eight teams play a match (or often two TIEs) to decide which four teams go forward to the NEXT ROUND
Rankings – A chart showing which teams are most likely to win a championship, often used to make sure that all the best teams are not put in one GROUP
Rapport- How well players or a whole team understand each other, e.g. being able to ANTICIPATE each other’s moves. Often used about an important PARTNERSHIP
Read a pass- Know where and when a PASS is going to end up
Real Pronounced like “rey-al”, this is the usual way of referring to Real Madrid in English-speaking countries. In Spain, Real Madrid is simply “Madrid” (Atletico Madrid being “Atletico”), while “Real” is short for Real Sociedad.
Red card- The ultimate punishment, meaning that a player has to leave the PITCH for the rest of the game and usually also miss future games
Red Devils- Idiotic nickname for Manchester United and the Korean NATIONAL SIDE
Reduced to ten men- Playing with only ten people in your team after a RED CARD, usually making it difficult to win the game
Ref- A common short form for REFEREE
Reflex shot- A SHOT kicked with no time to consciously plan what you are doing, e.g. a VOLLEY
Reflex save- A save made without any time to plan, e.g. the GOALKEEPER diving in the wrong direction during a PENALTY but sticking his leg up to save the ball
Regional championship- A competition between the best sides of the same continent or region, for example the European CHAMPIONS LEAGUE
Regular first-team place- Usually being picked to play in the SENIOR TEAM,the aim for most players
Regular season- The dates that most teams will have to play games, e.g. between September and April or May in most European countries. The dates for PLAYOFFs, the CHAMPIONS LEAGUE final, WORLD CUP etc are before or after this, so are said to fall outside the regular season
Regulation ball- A ball that has been certified by FIFA for use in official matches, and therefore good practice to play with when the regulations are changed or if you want to play professional football
Regulation pitch- A PITCH whose size is within the limits set by FIFA, and so good practice for top level football. Similar to “Olympic size swimming pool” in swimming
Regulation time – 90 minutes, to which INJURY TIME is added to decide on the actual length of the match
Relegation battle- (1) Have to make a great effort not to be RELEGATED (2) A match with another team who might also be RELEGATED, i.e. a SIX POINTER
Relegation- Being forced to go down to a lower DIVISION, e.g. due to being the bottom team at the end of the SEASON or losing the PLAYOFFs
Relegation zone - The places in the TABLE which will mean being RELEGATED to a lower DIVISION or having to go through PLAYOFFs to STAY UP, e.g. the last four teams out of a 16 team division
Replay- (1) Showing a part of the match again on TV (2) Playing the same match again, for example because the original match had to be ABANDONED
Reserve team - See RESERVES
Reserves – A team of players who aren’t able to enter the SENIOR TEAM due to not being IN FORM etc, who often play against reserves from other clubs for practice, sometimes in a dedicated league.
Restart- Start a match again which has been paused due to things like bad weather, the SPOTLIGHTS going off, or a PITCH INVASION
Right wing- Playing on the right edge of the pitch (from your own perspective), near the TOUCHLINE
Robbed- The expression “We were robbed” is often used to say that bad refereeing decisions were they only reason we didn’t win a match
Rock-solid- Used to describe a DEFENSE that it is impossible to get the ball past, like trying to get through a rock wall
Round robin play – Where every team plays every other team
Runners up medal- An award for the RUNNERS UP
Runners-up – The second placed team in a DIVISION or the losing team in a FINAL
Running off the ball – See OFF THE BALL

The index of all previous and future letters in this soccer lexicon are here: