Trainer was at Blue Square Premier side Oxford last season
AFC Telford midfielder Phil Trainer scored the only goal as the Bucks reached the FA Cup fourth qualifying round at the expense of Worcester.
Telford took a deserved lead in the replay after 23 minutes in front of just over 1,000 fans.
City fought back in the second half but could not break down a stubborn United defence at St George's Lane.
The Bucks now travel to the winners of next week's Blyth Spartans-Salford City replay for a place in the Cup proper.
City manager Richard Dryden told BBC Hereford and Worcester: "First half we should have been out of the game, but I am proud as punch of our second 45 minutes.
"They could have been two goals up. Second half, we came out of the blocks and they were on their last legs.
"They are good players, and the work-rate we put in was exceptionable.
"We were not favourites to go through in the tie, but we should have got something out of it.
"It's disappointing for me and the board. They would have been looking at that £7,000 figure."
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