Yo Mahesh struck in the ninth over to dismiss Ajinkya Rahane (17) and reduce hosts Royals to 40/3 in 8.4 overs.
The match was marred with rain interruptions.
Play resume after rain stopped the crucial match for the second time soon after the hosts lost skipper Dravid.
Hilfenhaus gave the visitors early breakthrough as he dismissed Dravid in the second over to reduce the Royals to 6/1 in 1.5 overs.
The important IPL clash was stopped for almost 50 minutes by light drizzle soon after Chennai pacer Albie Morkel bowled the first ball of the match.
Earlier, Chennai skipper MS Dhoni won the toss and decided to field against Rajasthan.
“With the rain around we chose to field as we want to have a better idea of the target,” Dhoni said after winning the toss.
Chennai have left out S Badrinath and Faf du Plessis, who are not well. Michael Hussey and S Anirudha will replace them in the playing eleven.
Rajasthan have made just one change in their playing eleven from last game, bringing in Brad Hodge in place of Owais Shah.
Upbeat after their two consecutive victories, Rajasthan are aiming for a hat-trick of wins and inch closer to a playoffs spot against an insipid Chennai.
Rajasthan have the winning momentum with them and have emerged from the shock of four consecutive defeats by posting two impressive wins over Kings XI Punjab and Pune Warriors.
The match will be a keenly-fought contest because a defeat in the match might just spoil the chances of either team to make it to playoffs.
The team composition for the previous two matches has been remarkable for Rajasthan. With Australian all-rounder Shane Watson and pacer Shaun Tait in the side, they have proved that they are better as a team than their more fancied rivals.
On the other hand, champions for the past two years, Chennai have not been in prime form this season and are languishing at sixth with five victories and six defeats.
They have not been able to finish off close games and have lacked consistency.
But Chennai have enjoyed a three-day break which might have provided them with enough time to regroup and plan for their remaining four games. The fact that they are the most successful IPL team, having played in three finals and have been victorious twice, should also give them confidence.
Besides, Mahendra Singh Dhoni leads a team that boasts of several international stars who have the ability to turn games.
Chennai Super Kings: Mahendra Singh Dhoni (capt/wk), Srikkanth Anirudha, Ravichandran Ashwin, Dwayne Bravo, Ben Hilfenhaus, Michael Hussey, Ravindra Jadeja, Yo Mahesh, Albie Morkel, Suresh Raina, Murali Vijay.