Hello thmh,
Logically if Manchester United should become "MancheU" then Newcastle United should become "NewcasU" but if you want it to be "Newcast" then I suggest you'll have to explicitly specify the "translation" for each team.
On the attached I used a lookup table, named Teamtable, to list all Premiership teams and the translations. You can change them as required. Note I left Fulham as "Fulham" which only has 6 letters, does it need to be 7? What would that be?
Then in Sheet2 A23 formula can be
=IF(Sheet1!B2="","",VLOOKUP(LEFT(Sheet1!B2,FIND(" v ",Sheet1!B2)-1),Teamtable,2,0))
and in C23
=IF(Sheet1!B2="","",VLOOKUP(TRIM(REPLACE(Sheet1!B2,1,FIND(" v ",Sheet1!B2)+2,"")),Teamtable,2,0))
Note: all games must include " v " otherwise the formula will fail, see attached
regards, barry