The set piece has been a real concern for Warren Gatland's outfit in several of their warm-up matches Down Under, which has been noted by a number of the players.
However, Greenwood feels that this could possibly be a secretive ploy but remains certain that the tourists must improve if they are to avoid defeat.
"This has been the one area of genuine concern for the Lions in the tour so far, but this may have been down to a genuine fear that they would give too much away if they showed their Test-match patterns in the warm-up games," Greenwood wrote in The Telegraph. "They will have been very aware of every lineout being filmed, of every call being recorded and wary of code breakers sitting long into the night trying to crack their systems.
"So much analysis has been undertaken by both teams in the build up and any clues will have been treated as gold dust. If a side is unable to control their own ball in Brisbane they will be dead in the water.
"You can let the opposition see how you ruck, maul, kick, pass and there is no real drama. Give them an insight into the lineout and it is game over, especially as the scrum has become such a lottery in terms of how it is refereed. The Lions must show improved accuracy when they are in Australian territory otherwise there is no point having monster backs."
The Lions face the Wallabies in Brisbane on Saturday.