Jofra Archer lives in extremes on the field. Sometimes he barely reacts to taking a wicket, at other times he runs wild in celebration. He bowls at 145 kph with the new ball, but slows it down under 120kph in the death overs.

These traits were on display at the Wankhede Stadium soon after Rajasthan Royals opted to bowl against Mumbai Indians. Archer was given the third over, just as Mumbai's openers had begun to attack, and his first delivery - to fellow West Indian Evin Lewis - was a short one sent down at 147.1 kph. Another short ball followed - 146.7 kph - and Lewis, beaten for pace, wore it on his thigh pad after he had left the first one alone.

Such was his confidence that while bowling around the wicket to a left-hand batsman, Archer brought in a second slip. After a wide delivery, Archer beat Lewis for pace again - 145 kph - and hit him on the arm. The barrage of short balls from one West Indian to another was a sequel to the Andre Russell-Chris Gayle battle the previous evening. When Lewis swung the next ball high into the Mumbai skyline and was dropped by Stuart Binny at mid-on, Archer barely reacted: a small drop of the head and back to his run-up.

Archer got his second over after the openers had put on 86 in the first ten. Once Suryakumar Yadav came on strike, Archer bowled a short one at 143.5 kph and, hurried for time, the batsman skewed a catch to Jaydev Unadkat long leg. A small reaction from Archer - regular high-fives - and he walked towards Unadkat for more subdued celebrations. That was the sedate Archer.

Next ball, Archer welcomed the Mumbai captain Rohit Sharma, who pulls well, with a short one at 143.7 kph. Rohit, a little off balance on his back foot, pulled it absolutely flat and hard to Unadkat again. Catch taken, Unadkat was still lying flat on the ground in disbelief because of how quickly the ball had travelled to him. Archer, however, had taken off. Running alone towards third man, hand in the air, thick gold chain jangling around his neck, and a beaming smile on his face, Archer found K Gowtham and did a little jig.

Archer's figures read 2-0-7-2 but Ajinkya Rahane resisted the temptation to give him another over because he was needed at the death. Archer came back in the 16th over; the ball was only five overs older but he knew he had to change tactics because Mumbai - only four down - were looking to accelerate.

This time, his regular deliveries were about 140 kph but he bowled a lot of slower balls under 120 kph. Archer also varied where he pitched the ball, making it hard for the batsmen to read changes in both speed and length and exploit the short boundaries.

It worked wonders. Hardik Pandya likes to swing hard at anything pitched close to him, but Archer made sure he was either fast and tight outside off stump, or much slower and short of a good length. Hardik finished on 36 off 21 balls, but had scored only five singles off six balls from Archer.

"In India you just can't blast people [with pace] all the time," Archer told Star Sports after the match. "So, you got to learn some variations, you got to get smart. The yorker is a highly risky ball so the margin of error is very small. With the slower balls, you can get away even if it's not perfect, so the margin of error is a lot bigger."

Even though Archer possesses a quick and mean yorker, he did not use it against Mumbai on Sunday, like he had against Chennai Super Kings two nights ago.

In that match, Archer bowled a mix of wide yorkers and short balls to concede only 12 runs off eight balls to MS Dhoni, and that included an inside-edged boundary. Archer perhaps knew that Kings XI Punjab seamer Mohit Sharma had denied Dhoni while defending 16 in the last over almost a month ago, and he did the same.

But Archer used different tactics - primarily bounce with his high-arm action - to finish with 4-0-16-2 against Mumbai. Allrounder Ben Cutting said after the match that Mumbai had been 20 runs short. If not for Archer, they might have scored 200.

Archer had been the difference in Royals' first match against Mumbai this season as well, his IPL debut. In that fixture, Suryakumar and Ishan Kishan had powered Mumbai to 130 for 1 in the 15th over before Archer bowled effectively at the death, taking three wickets in the 19th over. He kept them to 167 in that home game, and to 168 in the away leg.

"I think we've got the momentum now and there's no reason why we shouldn't make it to the playoffs," Archer said.

From being near the bottom of the league not long ago, Archer, along with Jos Buttler, has given Royals a shot at the playoffs. They are presently fifth, level on 12 points with two teams above them. Just like Archer's variations in speed, Royals will hope he can take them from one extreme to another in the league.

Vishal Dikshit is a senior sub-editor at ESPNcricinfo