They had their worst IPL season - finishing seventh - in 2020, and as the Chennai Super Kings look to bounce back and add to their three titles, they have received a shot in the arm in the form of Suresh Raina and Ravindra Jadeja joining their bio-secure bubble in Mumbai this week. While Jadeja linked up on Friday, Raina had joined on Wednesday. Both of them will undergo a week-long quarantine before joining the team's training, which takes off on Saturday.

For Jadeja, the IPL will mark a return to cricket since he dislocated his left thumb while batting in the Sydney Test against Australia in early January. Jadeja underwent surgery in Sydney before heading to the National Cricket Academy in Bengaluru to complete his rehabilitation. The injury had ruled Jadeja out of the all-format home series against England.

Earlier this week, Jadeja posted a video from the NCA, showing him holding the bat and bowling for the first time since the Australia tour. The franchise had originally expected Jadeja to join in the first week of April, but his early release from the NCA has ensured that he gets at least a week of training before the Super Kings play their first match of the season, against the Delhi Capitals in Mumbai on April 10.

'Tell them, I have come back'- Raina

While Jadeja would be expected to settle in quickly, the focus is bound to remain on Raina, who entered the Super Kings hotel quietly on Wednesday. This, in a way, is Raina's re-entry to the Super Kings ranks following a controversial exit on the eve of the 2020 IPL.

The Super Kings tweeted a picture of Raina in his hotel room with a title saying: "Vandhutennu Sollu! From namma Chinna Thala!" That translates to: "Tell them, I have come back", a line from Kabali, the popular Tamil film.

While there were questions about Raina's future with the franchise following stern comments from franchise owner N Srinivasan after the developments last season, Raina was retained ahead of the 2021 auction. Raina, who retired from international cricket along with MS Dhoni on August 15 last year, has kept himself fit by turning out for Uttar Pradesh in the Syed Mushtaq Ali Trophy.

Raina's return restores the balance in the batting department for the Super Kings, who struggled to find momentum until the latter stages of the league phase in 2020 IPL.

Dhoni & Co to begin training at Brabourne

It was also a particularly bad season for Dhoni the batsman, as he struggled to get into any sort of rhythm, scoring just 200 runs in 12 innings at a strike rate of 116. As he signed the yellow No. 7 jersey for players for rival teams, speculation grew whether he would be retiring after the season.

"Definitely not," he said after the Super Kings' final match last season, to put an end to the speculation.

Dhoni reached Chennai to be part of the preliminary training camp, which comprised a small group of mainly uncapped Indian domestic players. That camp was also conducted in a bio-secure environment with everyone involved adhering by the mandatory quarantine protocols set by the BCCI.

Kasi Viswanathan, the Super Kings' chief executive officer, told ESPNcricinfo that the players and coaching staff who were part of that bubble wouldn't need to undergo the seven-day quarantine in Mumbai. "Our first day of practice will be tomorrow (Saturday)," Viswanathan confirmed, revealing that the first two training sessions would be at Brabourne Stadium.

Ngidi to arrive on April 5

Head coach Stephen Fleming and assistant coach Michael Hussey are among the overseas members of the set-up to have reached Mumbai already.

Viswanathan confirmed that Faf du Plessis would arrive on March 26, and it is understood that Lungi Ngidi would be released from the ODI squad - along with other IPL-bound players - for the series against Pakistan on April 4, the day of the second of three games.

The Super Kings are one of the four teams - along with the Capitals, the Punjab Kings and the Rajasthan Royals - who will play the initial part of the league phase in Mumbai.

Nagraj Gollapudi is news editor at ESPNcricinfo