The New Saints saw their hopes of Champions League progress dented after a 2-0 away defeat against Croatian side Rijeka in the first leg of their second qualifying round tie.
Scott Ruscoe's side had beaten Gibraltar champions Europa FC in the first round, although they needed an extra-time away goal from Scott Quigley to secure a 4-3 aggregate win.
The Welsh Premier League side were soon trailing in Croatia when midfielder Josip Misic netted a fine 20-yard free-kick, clipping the ball over the wall and into the top corner in the fifth minute.
Rijeka, who were given a bye straight into the second qualifying round, doubled their advantage through substitute Florentin Matei after 69 minutes.
Quigley lashed a late angled shot into the side-netting as TNS were left with it all to do in the second leg at Park Hall.
Rijeka, who had ended Dinamo Zagreb's run of 11 league titles to secure the club's first championship, were good value for their early lead. Only a smart save from TNS goalkeeper Paul Harrison prevented Mario Gavranovic from making it 2-0 just before the break.
The home side threatened again early in the second half when Montenegro international Marko Vesovic drilled the ball wide from 20 yards before a deflected shot dropped inches past the far post.
When TNS did manage to relieve the pressure with a rare break, Quigley saw his shot fly off target.
Rijeka eventually doubled their lead when substitute Matei swept in a low cross from right-back Stefan Ristovski.
Quigley then had a chance to net a potentially crucial away goal when he latched onto a flicked header as the Rijeka defence hesitated, but his touch into the penalty area was too close to goalkeeper Simon Sluga.
Romanian midfielder Matei was denied a second goal by a fine save from Harrison, before Quigley crashed the ball into the side-netting after a late break down the left.