Kusal Mendis' recent string of poor scores may be a result of mental fatigue. That, at least, was the diagnosis of batting coach Avishka Gunawardene, ahead of the fifth ODI against India. Though he hit an excellent hundred in the second Test at the SSC, Mendis is yet to make a substantial impact in the ODIs, producing scores of 36, 19, 1 and 1.

This is despite Mendis' having begun his ODI career well - hitting 11 fifties and a century in his first 28 innings. In his last eight knocks, however, Mendis has returned five scores of one or zero.

"We had a chat about Mendis after the last game, and we feel that he is mentally drained," Gunawardene said. "He is still 22 years old. It's nothing to do with any technical issues. We will see what the management comes up with. I think it's better to give him a break before the next tour rather than keep playing him throughout."

Mendis has more reason than any of his teammates to feel a little weary of Sri Lanka's very busy schedule. Although he is often the youngest man in Sri Lanka's XI, Mendis has made 62 international appearances - including 17 Tests - since the start of 2017. That is five more matches than any of his teammates have managed. Incredibly, that is without having debuted in limited-overs cricket until the middle of last year.

Gunawardene believes Mendis should be deployed more sparingly, given his age and the stage of development he is at. "Personally, I think someone who is young like that should only be playing the longer version of the game and ODI cricket," he said. "I would rather keep him out of T20 cricket. He is still a player who is developing. Obviously we are looking at having him around for the next so many years. Better keep him for the longer formats - that's my personal opinion."

Elsewhere in the top order, Sri Lanka have more problems to solve. They have not passed 250 once in the series, and even batsmen who did score runs have largely played laboured innings. None of Sri Lanka's four half-centuries in the series have come at quicker than a run-a-ball.

"Dot balls have become a big issue for us," Gunawardene said. "Our dot-ball ratio in the last 12 months is something like 145 in a game. That is almost 50 percent, and that is one area we have rectify. We have set a target to improve that area by about 15 percent. We are trying to see whether we could improve our singles ratio while cutting down on dot-ball ratio.

In fact, Sri Lanka's dot-ball percentage in this series is even higher than those figures - they have not scored off 57% of the balls they have faced. India's dot-ball percentage, meanwhile, is 47%. Though the teams are neck-and-neck in terms of dot balls faced in the first 10 overs, India are much better at rotating the strike through the middle. Sri Lanka have also had issues putting partnerships together.

"Another target is that we try to tell the top five that someone has to bat for 45 overs. Then batting partnership is something that we have also spoken about - where we ask players to give us one 100-plus stand and one 75-plus stand. If we can do that the batsmen are capable of getting a decent score."

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando