It could not be more obvious that this game is the hasty post-script to to the tour. The two Tests came first and were always going to be taken very seriously. The five-match ODI series took 17 days to complete, because at least one of the teams wanted to have three days in between matches, to recover and prepare. This game is shoehorned in at the back-end, set to begin less than 48 hours after the last ODI was completed. Sri Lanka had a light training attended by only five players on match eve, and had made two late changes to their squad, instructing legspinner Jeffrey Vandersay and seamer Shehan Madushanka to stay with the emerging team currently involved in a limited-overs series elsewhere on the island. They have drafted in quicks Kasun Rajitha and Isuru Udana in their places. South Africa, who have not named a separate T20 squad, and will just pick from their ODI squad, did not train at all.
And yet - here's something that lays out just how beloved the format is by the in-ground spectator - this is the only match of the whole tour that will be played to a completely packed audience. On the eve of the match, SLC was all out of tickets. Colombo residents were making inquiries on the black market, and buying themselves new replica kits. With two years left until the World T20, the teams may not be taking this very seriously, but fans do not care.
As far as T20 form goes (insofar as form actually exists in a format that is infrequently played), South Africa may have a slight edge, having won three of their last five matches, to Sri Lanka's two. But then they are without two of their best bowlers in the format, with Chris Morris and Imran Tahir both elsewhere. With Sri Lanka riding a little wave of confidence following wins in the last two ODIs, perhaps the teams go into this evenly matched.
Sri LankaLLLWW (last five completed matches, most recent first)
South Africa LWLWW
In the spotlight
Acting captain Quinton de Kock did just about everything in his power to keep South Africa in the last ODI. He took three catches behind the stumps, and played by far South Africa's best innings, contributing 54 while seeming to actively shield the struggling Aiden Markram from spin early in the innings. His first two brushes with captaincy having led to losses, he will perhaps be relieved to hand the reins over to JP Duminy for the T20.
There was once a time when you could just about guarantee that Thisara Perera would be in demand in almost any T20 franchise in the world, and yet, this year, he could not land an IPL deal, nor did he play in Australia's Big Bash League. This dip in desirability corresponds to a nosedive in his form, between 2016 and 2017, but this year Thisara seems to be a new man. In seven T20 internationals this year, he has struck at 179 with the bat, with an average of 45.20, and though he hasn't quite turned it around with the ball in T20s, he has generally been good in ODIs. This one-off game may mean little to the Sri Lanka team in the grand scheme, but it is an audition for individuals hoping to land franchise deals.
It is possible South Africa will rest Hashim Amla, who has played every game on tour so far. Kagiso Rabada may get another break as well.
South Africa (possible): 1 Quinton de Kock (wk), 2 Reeza Hendricks, 3 Aiden Markram, 4 Heinrich Klaasen, 5 JP Duminy (capt), 6 DA Miller, 7 Wiaan Mulder, 8 Andile Phehlukwayo, 9 Junior Dala, 10 Lungi Ngidi, 11 Tabraiz Shamsi
Sri Lanka's XI is tough to predict - they may push Kusal Mendis up to open alongside Kusal Perera, as they have in T20s earlier in the year. Dinesh Chandimal, whom coach Chandika Hathurusingha believes can reignite the aggressive vein in his batting, may play as well. On the fast-bowling front, Sri Lanka will have to weigh up whether to give Lahiru Kumara a T20 debut, or play Kasun Rajitha, who has been impressive anytime he has been given an opportunity.
Sri Lanka (possible): 1 Kusal Mendis, 2 Kusal Perera (wk), 3 Upul Tharanga, 4 Dinesh Chandimal, 5 Angelo Mathews (capt.), 6 Thisara Perera, 7 Dasun Shanaka, 8 Isuru Udana, 9 Akila Dananjaya 10, Lakshan Sandakan, 11 Kasun Rajitha
Pitch and conditions
Expect a flat T20 pitch, though given this is Khettarama, there will always be some turn. There is some rain predicted, but showers at this time of year generally do not last long, if they arrive at all.
Stats and trivia
- Sri Lanka thrice failed to defend scores at Khettarama during the Nidahas Trophy earlier in the year, even losing after posting 214, against Bangladesh.
- South Africa have won five of the nine T20s between these two teams, including three of the four matches on the island.
Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando