Professor John Curtice of Strathclyde University said both sides ''have the right actors for the parts they're being called upon to play'' in the TV debate.
"The Yes side have one of the most charismatic politicians in Scotland, while the No side have one of the dullest in the United Kingdom," he said.
Curtice added that the chair of Better Together should make the most of his natural dullness and be "as boring as possible" if he wanted to deny the Yes side any sense of excitement or momentum.
Instead of offering fireworks, the former Labour chancellor should "play a dead bat", he added.
The latest poll of polls puts No on 57% and Yes on 43% among decided voters, meaning Darling has the most to lose from the debate, while Salmond needs to persuade people to back Yes.
Tuesday's clash, which Yes sources describe as the biggest moment of the campaign so far and the best opportunity to reach viewers without media bias, will be broadcast live on STV at 8pm.
Salmond and Darling will debate at the Royal Conservatoire of Music in Glasgow in front of a 350-strong audience made up of 40% Yes supporters, 40% No supporters, and 20% undecided.
After opening statements of two minutes and questions from STV political editor Bernard Ponsonby, the pair will cross-examine one another for 12 minutes each.
There will then be around 35 minutes of questions from the audience, followed by closing statements of one minute each.
Coin-tosses decided that Salmond would speak first and last on the two-hour show, with Darling conducting the first cross-examination.
The last half-hour will switch to a "spin room" of pundits and spokespeople from the two camps.
Yes Scotland is supplying independence supporters with "party packs" to help them host debate-night social events with undecided friends.
Curtice said political TV debates do not usually make a difference, though there were exceptions, such as Nick Clegg getting a boost in the 2010 General Election, and President Obama going backwards after a dire performance in his first debate against Republican challenger Mitt Romney in 2012.
Curtice said: "It's clearly a big event and it's clearly true the Yes side need it to make a difference. All Alistair Darling, frankly, needs to do is try and hang on to what he's got."
He said Salmond should avoid the aggression he uses to bulldoze opponents at First Minister's Questions, and instead look into the camera to reach voters who are minded to stick with the Union and "persuade them to take a punt".
As for Darling, Curtice said: "I would say to him, play to type and make this as boring as possible … play a dead bat. It's not to Darling's advantage to up the ante. You need to think of this as being like the second leg of a European cup match in which one side is already 2-0 up and is therefore trying to stop the other side from scoring."
Better Together sources indicated Darling and his colleagues have been immersed in what they call "debate camp" for several weeks, preparing for the encounter.
It is understood Salmond has been preparing for around a week, helped by Claire Howell, a lifestyle coach who helped him in the run-up to the 2007 and 2011 elections.
He has also been getting advice from former SNP MSPs Andrew Wilson and Duncan Hamilton.
The focus has been on how to connect with the TV audience, rather than jousting with Darling. The group will hold a further practice session in Glasgow this afternoon.
A spokesman for the First Minister said: "This debate is a fantastic opportunity for the Yes campaign's positive message to reach every home in Scotland - we know when people engage with the issues and listen to the arguments they come down strongly in favour of a Yes vote."
Better Together did not comment yesterday.