The Welsh champions lead by a goal ahead of the second leg, after which the winners will advance to a second round encounter with either Norway's Bodo/Glimt or Faroese outfit KI; the losers being consigned to the Europa Conference League.
Match preview
Last week's first-leg loss in Oswestry saw Linfield's hopes of progressing to the second round of Champions League qualifying take a serious blow, following their 1-0 defeat to The New Saints.
Ryan Brobbel's second-half goal separated the sides at Park Hall, and gives the Cymru Premier club a narrow advantage heading into Wednesday's return fixture in Belfast.
Both Jordan Stewart and Stephen Fallon spurned late chances for the Blues, being denied by Saints goalkeeper Connor Roberts, as the South Belfast side lost for the first time to opponents they have played three times before without defeat.
Linfield's pre-season schedule continued at the weekend, with a 2-1 win over NIFL Championship side Knockbreda FC, from whom long-serving coach David Healy signed young forward Ethan Devine back in January.
Under the management of one of Northern Ireland's greatest strikers - who scored 36 international goals before leading Linfield to five titles in the last six seasons - Devine played a crucial role in securing last term's NIFL Premiership title by a single point, just ahead of Cliftonville.
After claiming the club's 56th national crown, thoughts naturally turned towards another continental campaign, but the Blues have plenty of work to do if their current Champions League journey is not to be curtailed at the first hurdle.
The New Saints stand in their way, and recent European adventures have bred hope in the Welsh champions' camp: they have reached the third qualifying round of either the Europa League or Europa Conference League in three of the last four years.
After sealing a domestic double with victory in May's Welsh Cup final, Saints were soon back in training for their latest crack at the Champions League - a competition in which they have never before reached the group stage - and pre-season results indicated their readiness for last week's opener.
Two wins from two in their first pair of friendlies - a 5-1 victory over last season's Cymru Premier runners-up Bala Town and a 2-1 success against Cliftonville - were followed by a 2-0 loss to Larne in their final warm-up game.
Head coach Anthony Limbrick - the first Australian to lead a European club team to their national title - has already accrued some experience of continental competition, and during the inaugural season of the Conference League, his side progressed through the first two qualifying rounds.
Despite beating Linfield's old rivals Glentoran and FK Kauno Zalgiris, penalty shootout heartbreak was to follow in the third round, against Czech club Viktoria Plzen. Embarking on a similar run this year, though, relies on Saints retaining the slimmest of first-leg advantages.
Linfield Champions League form:
Linfield form (all competitions):
The New Saints Champions League form:
The New Saints form (all competitions):
Team News
After fielding several players who were still short of pre-season game time at the weekend, David Healy will revert to his strongest Linfield lineup for Wednesday's second leg.
Recent signing Robbie McDaid made his competitive debut for the Blues in last week's match, and Healy will rely on the former Glentoran striker to lead the line again at Windsor Park.
Two players who travelled to Oswestry but were not ultimately named in the matchday squad, Ross Larkin and Eetu Vertainen, will hope to be involved this time around - the latter has returned to Linfield for a second loan spell from St Johnstone.
The 23-year-old initially moved in January, with four goals from 10 games helping his new team win the title, and will now spend this season back in Belfast. He is still recovering from an injury sustained at the end of last season, though, so may only be fit enough to feature from the bench.
Meanwhile, TNS will again select Connor Roberts as their last line of defence, after the former Everton youth player starred in last Tuesday's win.
At the other end of the field, Scottish striker Declan McManus is set to start up front, having previously been named the 2021-22 Cymru Premier 'Player of the Season', with a total of 24 league goals.
Hoping to score in both legs of the tie, Saints winger Ryan Brobbel will start on the flank, back in the country he represented at Under-21 level almost a decade ago.
Linfield possible starting lineup:
Johns; Finlayson, Roscoe, Hall, Clarke; Shields, Mulgrew, Fallon; Cooper, McDaid, Millar
The New Saints possible starting lineup:
Roberts; D. Davies, Astles, K. Davies, Marriott; Smith, Routledge, Redmond, Brobbel; McManus, Cieslewicz
We say: Linfield 2-1 The New Saints (2-2 on aggregate; Linfield win after extra time and penalties)
The first leg result leaves this tie perfectly balanced, and there is every chance the game will go to extra time - particularly without the defunct away goals rule.
Linfield were denied by some sharp goalkeeping last Tuesday, but the support of the Windsor Park faithful can spur them on to score more than once. It may ultimately take spot-kicks to decide which side progresses, though.