Sri Lanka are seventh in the Test rankings, and have not won a match against top-nine opposition since August 2019. Bangladesh are ranked ninth and are coming off a difficult 2-0 Test defeat at home to West Indies. ESPNcricinfo looks at some of the biggest challenges the two teams will attempt to overcome through the course of their two-Test series in Pallekele.
Sri Lanka
Spin bowling
To win in Sri Lanka, spinners generally need to take a lot of wickets. One of Sri Lanka's problems has been that since the retirement of Rangana Herath, their spin attack has fallen away somewhat. Where their spinners collectively averaged 27.80 at home in Herath's last three years, they average 32.62 since his exit.
In this series, they will be without Lasith Embuldeniya, their most promising slow-bowling prospect, after he picked up a serious soft-tissue injury in the Caribbean. They are also without Dilruwan Perera, whose effectiveness had dipped substantially (he averages 32.17 at home since Herath's retirement in November 2018). They'll likely rely on wristspin via Wanindu Hasaranga or Lakshan Sandakan (or both), with Dhananjaya de Silva's offspin in support. But neither Hasaranga nor Sandakan have seemed up to leading a Test attack so far, partly because their control has been inconsistent between spells.
Although this series is being played in Pallekele where seamers may play more of a role than they do in Galle, Sri Lanka will likely need big wickets from the spinners too.
Batting collapses
Although since December Sri Lanka's batting has been sporadically impressive, such as in the first innings at Centurion or the second innings at North Sound, these successes have been interspersed with dramatic, harrowing collapses. In their last 12 Test innings, Sri Lanka have failed to make 200 on five occasions. Two of the worst nosedives came in their last series at home, against England, against modest bowling, when they were out for 135 and 126 - innings in which they surrendered the series. If they go into self-destruct mode again, they could cede another match.
Fitness
Coach Mickey Arthur has been adamant that players raise their standards, and have ruled certain players out of contention purely on fitness grounds. And still, Sri Lanka's long history with muscle and soft-tissue injuries continues to plague them. In addition to being without Embuldeniya in this series, they are also missing seamer Kasun Rajitha, while rookie batter Pathum Nissanka has been struggling with a niggle as well (but is expected to be fit for the series). There are many theories on why injuries seem to plague Sri Lanka more than most other teams. Some find fault with the conditioning, others point to a lack of recent cricket, or to developmental issues going back to the players' formative years. Whatever the case, rare is the series from which Sri Lanka emerge with all their key players intact.
Bangladesh
Overseas troubles
Bangladesh's Test record is such that it is considered inevitable they will not threaten on foreign soil. They have won only one away Test in the last five years, and since that one win, which came in Sri Lanka in 2017, they have lost each of their nine Tests on the road, all by heavy margins.
A big part of their problem is the inability to take 20 wickets abroad - a feat they have only managed five times in their history. Their spinners have been effective on favourable pitches at home, but these have left the fast bowlers with little to do. This lack of bowling at home translates into a lack of rhythm and effectiveness abroad. It has been eight years since a Bangladesh fast bowler won them an overseas Test.
The Shakib-sized hole
What would make it more difficult for Bangladesh in Sri Lanka this time is Shakib Al Hasan's absence. His stature as a Test allrounder makes him particularly difficult to replace. Mehidy Hasan Miraz performed admirably against West Indies recently but he has a lot to do to earn the allrounder's tag. This time the selectors have picked the 34-year old Shuvagata Hom as a batting allrounder when five years ago, during his last Test appearance, he was counted as a bowling allrounder. This is the sort of confusion that can arise when Shakib isn't around; no Shakib is always an advantage to the opposition.
Catching
Bangladesh's catching was one of the most worrying aspects of their disastrous New Zealand tour last month. They dropped ten catches in the ODIs and T20Is, which cost them results and momentum, and netted a bit of embarrassment as well. When the team returned from the tour, newcomer Nasum Ahmedoffered an explanation for the dropped catches that was the stuff of internet memes: "Their sky is very clear and their weather is nothing like ours."
The real story, however, was different. The 2-0 home defeat to West Indies in February shook the team, leading to a team-wide lack of confidence. As is often the case in cricket, this lack of confidence made for a poor fielding side.