On Monday the club took advantage of having no veterans on its list by promoting the two rookies, who were both taken in the 2008 NAB AFL Rookie Draft.
Harvey said the Fremantle coaches saw enough in de Boer's only pre-season match against Richmond to promote the All-Australian junior, while he described Broughton as uncompromising, resilient and tough.
"We think that they're physically prepared for AFL," Harvey said on Monday.
"We see those guys playing a role in the team, just through some physical attributes, before the other [rookies] at this stage.
"We'd like to think that they're both exciting young kids and that they can actually put enough pressure on the senior listed players, and you never know what'll happen throughout the course of the year."
Broughton, 22, has played in three premiership teams with WAFL side Subiaco since being overlooked by AFL clubs as a teenager. He won the side's club champion award in 2008 and represented WA at senior level.
Harvey said the medium-sized defender's senior experience would hold him in good stead in the AFL.
"Subiaco should be congratulated [on] the way they've developed him over the last couple of years," Harvey said.
"He doesn't get fazed by the game or who he's playing on. He's a foot soldier who you can rely on all the time”.
After playing a crucial role for WA in last year's NAB AFL under-18s Championships, de Boer blitzed the NAB AFL Draft Camp with top ten finishes in the 3km time trial, 20m sprint and 30m repeat sprint.
The 19-year-old has had a limited pre-season due to foot soreness, but Harvey said the prolific ball winner was already a mature footballer and ready for the AFL.
de Boer is a chance to play for Claremont in the WAFL this week, if the club gains AFL approval, while Garrick Ibbotson, Chris Mayne and Paul Duffield may also front up for their State league sides.
Harvey said a decision on the returning trio would be made after Wednesday's main training session, with Fremantle to open its season against the Western Bulldogs at Subiaco Oval on March 29.
Luke McPharlin, who has missed the last two pre-season matches after injuring an achilles tendon, will be ready for round one.
