The Lions throttled the Maori All Blacks in an imperious 32-10 victory in Rotorua on Saturday, but still left a host of fine line breaks unconverted.
Warren Gatland’s men strangled their hosts into submission, but England wing Watson conceded they must sharpen up behind the scrum.
The Lions will face back-to-back world champions New Zealand in the first Test at Eden Park next Saturday, with Bath flyer Watson calling on the tourists to add a lethal finishing streak.
“We need to finish off our line breaks and score tries from those,” said Watson.
“We have got to be better at finishing and not let it get to the case where moves break down and we receive penalties.
“That said, I think things are moving in the right direction. If you look from the first game of the tour to now, you can see there has been a drastic difference to how we play.
“That is credit to the coaches and the players for all buying into the ethos. Everyone is working hard to get everything in order. It has been great but there is much more to come.”
England’s playmaker Owen Farrell could yet shake off a quadriceps strain in time to start the first All Blacks Test.
Head coach Warren Gatland revealed the Lions only held Farrell back from action against the Maori as a precaution, and Watson hopes the focused Saracen could now hand the tourists a huge Test boost.
Farrell’s possible return to fitness would bolster Gatland’s midfield options to face the All Blacks. The England man could pair up with Johnny Sexton or slot in alongside battering-ram centre Ben Te’o.
Wales star Jonathan Davies, pictured, pulled off several eye-catching line breaks against the Maori, leaving Watson admitting the Lions now boast a promising mixture of backline options. “Having Owen Farrell fit and healthy would be a massive boost for the squad as well but we will have to wait and see,” said Watson.
“Johnny Sexton and Dan Biggar both played very well again out there against the Maori and competition for places is high.
“The way Ben Te’o is busting the line out there, maybe I will try and run off him more and exploit those line breaks.
“But either way, whoever they select it would be great to be outside them.”
While Watson was never able to cut fully loose in Rotorua, he admitted he will happily chase Conor Murray’s peerless box kicks all tour long.
“I have got to try and impact the game wherever possible and if that is chasing kicks then I am definitely happy to do that,” said Watson.
“From a winger’s point of view, what you want is your nine to put the kicks on the money so you can challenge for the ball or make a decent hit. And it’s an absolute joy to chase Conor’s box kicks.
“The forwards were outstanding: the maul was just going on and on and on and I was just chilling on the wing! For us backs to have that platform to play off is unbelievable.
“The mood is good right now but at the same time the All Blacks will be a huge step up, so we have to be ready for them.”