Hearts caretaker boss Locke said on Thursday that he believes the Tynecastle men are still the dominant force in the capital - despite failing to win any of the three meetings with their city rivals this term.
But, with the teams due to meet at Easter Road in Sunday's Clydesdale Bank Premier League clash, Fenlon said even Locke cannot deny just how well his Europa League hopefuls are playing.
He said: "I don't think anyone can doubt how far we have come. Over the course of this season we have shown that we are playing well and with confidence.
"When we came into the club, the object was to try to improve the team. Part of that was improving our record in derby games, which we have done slightly.
"We know there is still a lot of work to be done but we are making progress, which is important. We've got to continue to do that."
Both SPL Edinburgh derbies so far this season have ended in stalemates, but Hibernian did come out on top in their Scottish Cup fourth-round tie as a deflected David Wotherspoon strike brought Hearts' 12-game unbeaten streak against their Leith foes to an end.
Fenlon, however, fears that result - and his game plan - may end up counting for nothing once the frantic action gets under way.
He said: "With derby games, form goes out the window. We've done a lot of work preparing for how Hearts play but I know for a lot of players, once they cross that white line, a lot of that will go by the wayside.
"Once the first tackle goes in or something happens, the crowd will just carry people along.
"But over the last few weeks, our form has been pretty decent. We have passed the ball well and created chances and now we've got to make sure we don't get caught up on it all."