RCB has some extra all rounders than required, and lesser widely known batsmen than required, which makes the selection difficult. A lot has to be considered while selecting the XI, especially the Chinnaswamy pitch, which wasn't exactly the same in 2017 what it was a year ago. I hope the 2016 track is back.
This will be my XI if the pitch is unchanged from 2017:
Quinton de Kock
Manan Vohra/Sarfaraz Khan
Virat Kohli
AB de Villiers
Mandeep Singh
Pawan Negi
Corey Anderson
Chris Woakes
Umesh Yadaav
Yuzvendra Chahal
Mohammad Siraj
We have tried experimenting a young local opener with Gayle, but mostly we have failed in producing a good stand for first wicket, due to which Virat considered himself to open alongside Gayle. Also without Gayle, and a more consistent opener in the offer, I guess we can keep Manan Vohra and Sarfaraz Khan dedicated for the spot.
Virat and AB best fit at #3 and #4 in the line up, so they have their positions reserved, until something very unexpected happens with their performances.
#5, #6 again trusting on the young Indians in Mandeep and Pawan (backed up by Washington Sundar), because we have Corey and Chris coming after them. As long as they are not eating the balls for dinner or evening snacks, it should be fine. If the situation demands, probably we may send Corey Anderson at #6 and Woakes at #7.
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Colin de Grandhome will ensure that he's backing up Chris and Corey, in case if either of them are consistently failing, he'll replace them. If both of them fail to deliver, probably that is when Moeen Ali comes into picture, and that will also juggle the positions of the players a little.
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Bowling looks fragile, however, as I mentioned, with the assistance the Chinnaswamy pitch gave in 2017, Chris Woakes, Umesh Yadaav, Yuzvendra Chahal, Mohammad Siraj, Corey Anderson and Pawan Negi can handle the things.
The worst thing that can happen is Corey performing with bat and turning out to be a flop show with ball, which is when things get worst.
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Personal opinion: RCB should have invested on proven Indian local talent, like Manish Pandey, KL Rahul, and Robin Uthappa (I believe he wasn't retained by KKR, I welcome to be corrected) instead of investing on overseas players who probably won't see a game unless their plans drastically fail like Moeen Ali, Brendon McCullum and Tim Southee. Having additional options is wonderful, but not with overseas players. RCB has way too many back ups for overseas players, and very inexperienced Indian blood, which may back fire this time.