Cook was able to get into the habit of naming his team fully 24 hours in advance as England won the Investec series 2-0 against the same opponents.
But with rain disrupting practice at Trent Bridge – England had to net indoors for the second successive day – Morgan faces much tighter calls before he can announce his XI for today’s first one-day international.
Ben Stokes’s injury-enforced absence from the Royal London Series is part of Morgan’s problem, as is the conundrum of how to find room for in-form batsman Jonny Bairstow, of Yorkshire, to return for his first ODI since the end of last summer.
England can hardly turn their nose up at Bairstow’s prolific run-making over the past 12 months, but Stokes’s unavailability means they may need to sacrifice an extra bowling option to shoehorn the Yorkshireman back into the team.
Morgan gestured up to the skies and across to a square under full cover with rain falling as he explained tricky decisions lie ahead, saying: “A day where the wicket doesn’t see sunlight or fresh air can create a dilemma in selection, so I’m not looking to announce [the team] now.
“[All-rounder] Moeen Ali gives you the luxury of going either way, with bat or ball.”
Whoever takes the field, Morgan acknowledges further progress is needed despite England’s vast improvement in white-ball cricket since the start of last summer, including their run to the final of the ICC World Twenty20 under his captaincy.
“If you look at where we sit in the ICC (ODI) rankings, we’re actually below Sri Lanka and that’s a reflection of our performances over the last number of years,” said the Irishman.
As for England’s near miss in the World Twenty20 in India two months ago, he added: “I don’t know if it’s a springboard, but it’s certainly a huge confidence-booster. This is a key summer in that we’re 12 months down the road [following the 2015 World Cup], and we have built a lot of confidence.
“There’s a bit more expectation on us as a side, and it’s important to relish that expectation. We’re still at the beginning of building for what we hope will be a successful campaign in the 2019 World Cup.”
Sri Lanka have endured the shock of discovering over the past week that seamer Shaminda Eranga has an elevated heartbeat.
Captain Angelo Mathews says that further tests are being carried out.
England (possible): EJG Morgan (capt), JJ Roy, AD Hales, JE Root, JC Buttler (wkt), JM Bairstow, MM Ali, CR Woakes, DJ Willey, CJ Jordan, ST Finn
Sri Lanka (possible): A Mathews (capt), K Perera, D Gunathilaka, U Tharanga, D Chandimal (wkt), L Thirimanne, D Shanaka, F Maharoof, S Prasanna, S Lakmal, N Pradeep
Umpires: P Reiffel (Aus) and R Bailey.
Match referee: D Boon (Aus).