The lack of a killer edge leaves Dundalk with much work to do in the Skonto Stadium next Wednesday.
The Lilywhites had their chances in Oriel Park tonight but couldn't produce the cushion of at least one goal to take to the Latvian capital.
The loss of the hugely influential Chris Shields at the break after a clash of heads with team-mate Daniel Cleary certainly didn't help the cause, though Dundalk will still feel they have the quality to come through this tie.
Vinny Perth spoke on the eve of the game of this being the best Dundalk squad that he's worked with, a bold statement given the 2016 charge into the Europa League group stages and the team's performances therein.
For this first leg, Perth started four experienced players from that run on the bench - Brian Gartland, Dane Massey, Robbie Benson and Andy Boyle - thus keeping faith with the group that had extended the club's unbeaten run to 16 games.
Dundalk mixed up their attacking game in the opening period, gaining most traction down the right where Sean Gannon and John Mountney caused a lot of problems.
But the loss of Shields saw momentum shift to the visitors until Benson's introduction sparked the hosts back to life.
Gannon bombed forward from the start and within 40 seconds there was a flashpoint when he got in the way of Ritvars Rugins as he went to take a quick throw. The Latvian had a little kick out at the full-back.
It took just four minutes for Dundalk to produce their first chance, with Michael Duffy firing over the top from 20 yards.
The hosts were aware of Riga's counter-attacking threat but there was a moment of concern when Roman Debelko got in behind the Dundalk defence, but Shields snuffed out the danger.
Centre-back Sean Hoare had two very good opportunities midway through the half - the first was a header just wide from a Dean Jarvis corner.
The second materialised after Joel Bopesu slapped Gannon, who was in possession, in the face and Duffy's free was deflected to Hoare.
He did well to control the ball on the turn but then prodded wide.
It was almost the half hour mark before Riga put together a move of note but Roger couldn't muster the appropriate finish, shooting weakly wide.
Moments later, Patrick McEleney lost possession cheaply in the middle of the park and Olegs Laizans' low shot bounced in front of Gary Rogers, who got a touch and the ball squirted wide.
But Dundalk came close again in response, Mountney pulling back a low cross from the byline to Hoban. A crucial tackle by Herdi Prenga prevented a goal as it denied the striker full contact.
Then Hoban headed over from a Jamie McGrath delivery and, after the unfortunate clash of heads just before the break, he was replaced for the second half by Andy Boyle.
The recently re-signed Dubliner took his place at centre-back, with Hoare moving into midfield.
Debelko had a go from outside the box early on, his effort deflected around the post and but the arrival of Benson for Mountney.in the 58th minute got Dundalk shifting through the gears once more.
Within seconds, Duffy uncharacteristically wasted an opening - his attempt to curl a right-foot shot into the far corner skewed well wide.
The Lilywhites came forward again and McGrath danced his way into the box before shooting straight at Roberts Ozols, but in the 76th minute Hoare lost out to Laizans, Roger fed Bopescu but he shot wide with only Rogers to beat.
Dundalk had late chances through Duffy, who again shot wide, and Hoare's header.
However Lilywhites fans were on the edge of their seats in the closing seconds when Jarvis fouled Debelko.
Tomislav Saric couldn't steer his free-kick inside Rogers' near post and it's stalemate going into the deciding leg.
After the game, Sean Hoare told RTE: “We wanted to keep a clean sheet because we know if we go over and score one it makes it very difficult for them so it was important to keep the door shut here.
“I am kind of used to it at this club because I’ve played in all sorts of positions and I don’t mind once I’m out there. The main thing is that I’m playing.
“We did homework on them and they came here as we expected. We just weren’t good enough, we didn’t create that many clearcut chances. But, in saying that, we were disappointed not to score.
“It will be tough, it’s always tough travelling and being expected to perform at the highest level but we’ve done it before. This group has done it lots of time so we’ll settle down and prepare for the next leg".
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