Chennai recorded their sixth win as Santner's six sealed in a dramatic final over in which CSK needed 18 runs.
A clear waist high no-ball to Santner was ruled out by umpire Ulhas Gandhe after trying to raise his arm.
This prompted an angry Dhoni to enter the ground and literally blast Gandhe before leg umpire Bruce Oxenford calmed him and sent him back before Santner finished it off in style spoiling a brilliant outing from Jofra Archer (1/19 in 4 overs).
Dhoni-led Chennai faced some early blows. Opener Watson, who has not been in good form, was bowled by Kulkarni for a duck. Soon after, Archer got a stunning direct hit at the non-strikers end to dismiss and shock Raina at the same time as he was running quite casually, not expecting a spot on direct hit. After this, CSK were 5/2 as Rayudu walked to bat. However, Unadkat struck again to take out Faf and put Chennai in big trouble as they were 15/3 after four overs.
Chennai were in great trouble after losing four wickets that too in a power-play and RR’s Ben Stokes ensured that his squad completely dominate the visitors by taking the Catch of IPL 2019.
Dhoni on his part scored 58 off 43 and added 95 with Ambati Rayudu (57 off 47 balls) for the fifth wicket. However Stokes got Rayudu with a yorker.
Dhoni and Rayudu's 50-run stand for the fifth wicket came in 42 balls as Dhoni deposited Gopal into the stands for his third six. Rayudu also did his bit lofting Stokes for a six.
Earlier, Chennai Super Kings produced yet another disciplined bowling effort to restrict Rajasthan Royals to a modest 151 for seven.
Save Jos Buttler (23 off 10 balls) at the top of the order, none of other Royals batsmen looked the part as CSK skipper Mahendra Singh Dhoni's immaculate reading of the track once again helped the defending champions.