Littlejohn says the former Black Caps batsman seems vulnerable to fast bowlers.
Sinclair, he says, was told to work on that aspect of his game since he was released from the national team.
Admittedly the batsman has often rued missing his opportunities to make a fist of his international career.
He was also vociferous and critical, falling out of favour with national selectors.
The right-hander, who scored 214 on debut against the West Indies in Wellington in 1999 and followed it up with an unbeaten 204 against Pakistan the following season, has played 33 test matches, 54 ODIs and two Twenty/20 internationals.
Ironically his last taste of international cricket, albeit fleetingly, came on January 10, 2009, when the Windies dismissed him for two runs in a rain-abandoned fourth ODI match at Eden Park, Auckland.
Former Black Caps coach Mark Greatbatch had thrown him a lifeline after Jesse Ryder was stood down for breaking team protocol.
Littlejohn says it isn't NZ Cricket's style to hold grudges against players for criticising previous regimes.
With the Black Caps batting exposed in a T20 match in Sri Lanka this week critics have questioned the omission of 2011-12 NZ Cricket award winners Martin Guptill (Auckland) and Doug Bracewell (CD) who were left behind.
Resting a "jaded" Guptill, Littlejohn says hindsight is a good thing. Giving other players the chance to prove themselves in Sri Lanka, he says, was also a factor.
Bracewell had technical issues to resolve in the domestic environment.
"In the first innings he bowled seven no balls," Littlejohn says of the Taradale Cricket Club player who in one no-ball delivery gave Michael Papps a lifeline on Sunday after bowling the Wellington opener cheaply.
"He also bowled without some luck. Some of the batsmen weren't good enough to get an edge," he says, lauding Bracewell for his 85 runs at No8 in the second innings.
CD leg spinner Tarun Nethula, Littlejohn says, is a victim of not playing enough cricket while on the Black Caps' tour of West Indies and India.
"We left him out to play against India A and Tarun was struggling," he says, adding he also had to work on his technique with his coaches.
The Heretaunga Building Society Cornwall cricketer's bowling action has lately evolved into a medium-pace, front-arm action, as opposed to a leggie whose bowling arm winds up from the head.
Littlejohn says veteran New Zealand spinner Daniel Vettori is still some away from returning to the fold.