Not too long ago, Bhuvneshwar Kumar was among the first names in India's team sheet, particularly in white-ball cricket. Swing has always been Kumar's strength and without compromising on that, he cranked his pace up to 140kph and even proved deadly with the old ball. Such a varied skillset helped him emerge as the top wicket-taker in both IPL 2016 and IPL 2017. Then, in the Champions Trophy, Kumar was also India's leading wicket-taker, but multiple injuries, including one suffered during the World Cup last year in the UK, have pushed Kumar down the pecking order.

Kumar had briefly returned to action last year during the home T20I series against West Indies, but then a groin injury sidelined him from the following ODI series. Kumar's injury-enforced absence coincided with the rise of another swing bowler Deepak Chahar, who all but punched his T20 World Cup ticket to Australia, with a record haul of 6 for 7 against Bangladesh.

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However, Chahar is now on the injury list, while Kumar will reunite with Jasprit Bumrah, who had gone wicketless in three ODIs in New Zealand and is probably still finding his way back from injury.

Arguably, this is the first time in his career that Bumrah is going through a rough patch. Things haven't been hunky-dory for Kumar as well: aside from dealing with a surfeit of injuries, he has lost his place in the Test side. And on the whole, India's pace attack had a torturous shift in New Zealand. Shardul Thakur kept erring with his lines and lengths - and is now out of the squad - the pace and bounce of Mohammed Shami and Navdeep Saini couldn't bail India out either. The one key ingredient that was missing in India's attack was swing.

This is where Kumar comes back into the fray and could ease the pressure building on Bumrah in particular. Plus, he's the most experienced bowler in India's current white-ball group and the team management values that. Kumar and Bumrah have forged a strong partnership in the past, with India winning 31 of the 41 ODIs they have played together. Bumrah would get his exaggerated angle going and straighten the ball away from right-handers. At the other end, Kumar would swing it back into the right-handers, scrambling the mindset of batsmen in fairly contrasting styles.

Kumar wasn't at his best in the T20Is against West Indies last year, but if he can get the ball hooping in and out once again, then India's pace attack will be complete. And there's a good chance that the ball will nip around in the fresh mountain air of Dharamsala, the venue for the series opener against South Africa. In the last ODI played in Dharamsala, Sri Lanka's Suranga Lakmal exploited the swinging conditions efficiently to bundle India out for a mere 112 - their lowest total batting first at home. The pitch for the third - and - final ODI at Eden Gardens might also aid swing and seam.

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The challenge for Kumar is not his bowling as much as staying fit for longer periods. By his own admission, injuries over the last couple of years have affected his rhythm. A lower-back injury sustained during the ODI series in England in 2018 meant he missed the subsequent Test series. In the marquee clash against Pakistan during last year's World Cup, Kumar had to limp off after picking up a left hamstring niggle. His worth can be gauged from his return in the semi-finals against New Zealand where India opted to bring him back ahead of the in-form Shami. However, Kumar then suffered from sports hernia, which disrupted his rhythm and progress once again.

So it might be too much to expect Kumar to simply turn up and get that banana swing that made us all sit up and take notice of him. Recently, while speaking to ESPNcricinfo, former Australia seamer Glenn McGrath explained that bowlers usually need their own time to feel their way back from the sidelines.

"If you finish the season up here [indicating a high level with his hand], the next season you want to start back up here," McGrath said, alluding to Bumrah's post-injury phase in New Zealand. "It doesn't work that way and it took me a few seasons to work that out. I thought this is where I want to get to [the high level] and I'm starting the season again or coming back from injury, I'm starting down here [at a lower level]. So, I've to realise that and allow myself a few matches to get into where I want to get to and get on that upward slope. I think that's probably the biggest issue - the expectations from everyone, back in the team I've got to pick up exactly from where I left off."

Kumar only had a light workout prior to the South Africa series, participating in the DY Patil T20 tournament, an invitational event, in Mumbai. "It's difficult to maintain pace when you return from injury," he said on the eve of the series opener in Dharamsala. "The reason being that the possibility of getting injured again remains at the back of your mind, you worry that if you bowl at the same pace, you might get injured again. The best option is to play matches like I'd played a few matches before returning. You gain confidence from playing matches before the step-up. It's a challenge but there are ways - you have to go through rehabilitation and work with the physio but the best way is to play matches."

Kumar will now run into Quinton de Kock, who has a stellar head-to-head record against Kumar in ODIs. The South Africa captain has hit 151 runs off 146 balls against Kumar without being dismissed. To add to that, South Africa are coming off a 3-0 whitewash in the T20Is against Australia at home and will be bolstered further by the return of former captain Faf du Plessis.

Nonetheless, this series against South Africa and then the IPL will be of utmost importance for Kumar as India look to firm up their attack for the T20 World Cup later this year in Australia, where the ball might also swing.

March 11, 2020, 10:18 am GMT: The story was updated after Bhuvneshwar Kumar's pre-match press conference

Deivarayan Muthu is a sub-editor at ESPNcricinfo