Based on the evidence that
A- Thomas was a centre back, playing out of position at RB and was average at best.
B- Richardson is a right back by trade, and was in the L1 team of the year for last season, ie the best right back in L1, better than Thomas
C- Butterfield played at right back for a team the league above us, and had played the majority of his career at that level
D- Wayne Thomas is 31, a year older than Butterfield and 4 years older than Richardson, so that quashes your, players over 30 arguement.
I would say it is foolish to say that all of the above is speculation.