Di Resta endured a wretched end to last year, collecting just two points from the closing six grands prix, and in the final race in Brazil crashing out for the first time in his Formula One career.
With Di Resta out of contract with the Silverstone-based marque at the end of this season, the Scot knew he had to come flying out of the traps.
With 20 points from his first four grands prix, the 27-year-old has made his best start to a year since first arriving in F1 in 2011.
On Sunday in Bahrain, Di Resta came within a whisker of finishing on the podium for the first time in his 43 races, at least equalling his career-high of fourth.
Speaking to PA Sport, Fernley said: “He’s done a great job. He dusted himself down after what was, for him, a disappointing end to 2012, but with all due respect there were circumstances around that.
“We identified them, and credit to Paul, he accepted where those were — they were not really his issues — and he has come out fighting this year.
“There was certainly a bit of pressure on him at the start, but he’s stuck to his task, which gives you an idea as to the depth of Paul’s ability.”