While England are looking good as they aim for a 3-0 whitewash in the series, they need some reliability from their leading batsmen and captain Joe Root is backing Bairstow, who has lost the wicketkeeper's gloves to Ben Foakes, to succeed.
"One thing we all know about Jonny is whenever he's got a point to prove or is up against it, he generally comes out and does something pretty special," said Root.
"Hopefully we see that with Jonny this week -- that determination and drive to really hammer that spot home for himself. It's an opportunity for him to try and nail that spot down and he's more than capable of doing it."
The 29-year-old Bairstow had admitted his frustration at getting injured in training before the first Test of the tour and losing his place to Foakes.
"It's difficult. No one wants to not be playing," Bairstow said this week. "The last two-and-a-half years I've been in the team, and it was only three Tests ago I was in the top 10 batters in the world. And then you're not playing."
Foakes hit a century on his Test debut and has been outstanding as wicketkeeper, freezing Bairstow out of the reckoning. But England desperately need a reliable number three after Moeen Ali and Ben Stokes failed in the previous two Tests -- as did Root batting at four below a nightwatchman.
Root pointed out that England had still won both games, but acknowledged that he needs Bairstow to seize his chance.
"At the minute that (keeping wicket) is not an option for him in this team and I think it's a really good opportunity for him to take his batting to another level," Root said.
"It would be nice to see him really grab number three by the scruff of the neck and use it as an opportunity to start really consistently scoring big runs in this format."
Bairstow's return means that Stokes moves back down to number five, while England's other big change has been to rest fast bowler James Anderson to give Stuart Broad a chance.
Root said Broad, 32, remains "invaluable" to the England side even though he has been overshadowed by 36-year-old Anderson's feat in becoming the fast bowler with the most Test wickets.
"He's still one of England's best bowlers –- I genuinely believe that," said the captain, who will next take his squad to the West Indies this winter.
Broad will make his return on the Sinhalese Sports Club ground where he made his Test debut in 2007.
"We generally get very excited about wishing people retirement and I think with those two (Broad and Anderson) in particular we have to make the most of them while we can, be smart about managing them and see how long they can go for," said Root.
Sri Lanka called back opening batsman and part-time bowler Danushka Gunathilaka into their squad after his latest suspension for misconduct.
But skipper Suranga Lakmal said Gunathilaka was not certain to play though he admitted "our batting is in a little bit of a lull."
Sri Lanka will be without spinner Akila Dananjaya, while his suspect bowling action undergoes International Cricket Council tests.
With Rangana Herath now retired, Lakmal said missing the pair was "a big loss". He still wants a pitch suited to spinners prepared in Colombo.
Ben FoakesDanushka GunathilakaEnglandEngland vs Sri Lanka 2018Joe RootJonny BairstowMoeen Alisri lankaSri Lanka vs Englandsri lanka vs england 2018Suranga Lakmal
First Published: November 22, 2018, 7:40 PM IST