Chris Chester may have seen his side down to their last 17 available players - 16 once Matty Ashurst departed with a first half HIA - but they showed tremendous spirit to give the Super League champions a genuine fright.
Trinity had been 14-0 down at one point against opponents who, in contrast, were almost at full strength ahead of next Saturday’s Challenge Cup final with Castleford Tigers.
However, on-loan Huddersfield Giants winger Innes Senior, making his first appearance in nearly three months, scored a fine brace of tries to see Trinity trail the hosts just 16-14 in the 62nd minute.
Mason Lino’s touchline conversion struck a post and it was a sign of how much pressure they were applying that Lachlan Coote slotted a penalty soon after just to give Saints some semblance of relief.
David Fifita rumbled around causing all sorts of problems and the visitors’ discipline waned, England centre Mark Percival having been yellow carded for interference shortly before Ryan Hampshire’s splendid pass ushered Senior in for that second.
However, for all their possession, Trinity could not break them down again and instead Coote - the Australian full-back who this week announced he will join Hull KR in 2022 - finished them off in the 64th minute, supporting Sione Mata’utia’s stylish break.
He also maintained his 100 per cent kicking record with his seventh goal when England winger Tommy Makinson crossed in the 79th minute.
Played in filthy conditions, Trinity winger Liam Kay had to come on at hooker for most of the game such were Trinity’s personnel issues but he adapted well.
Wakefield went in 16-10 at the break having scored with their only two genuine chances of the period.
Saints initially controlled the ball better in the rain and went ahead when Percival hit Coote’s double-pump pass which fooled Trinity’s defence in the 13th minute.
The hosts also lost forwards Tini Arona and Ashurst to HIAs within the space of 60 seconds before Coote added a penalty.
Kristian Woolf’s side were further encouraged when Lee Kershaw fumbled playing the ball in his own half but there was no excuses for the dismal defensive effort that followed.
Saints half-back Lewis Dodd received the ball from a standing start 10m out yet was easily allowed to sidestep and waltz his way through some woeful tackling for Coote to convert for 14-0.
Nevertheless, Makinson spilled in the restart set to hand Trinity a rare opportunity and they gladly made the most of it.
Fit-again Jacob Miller, Lino and Reece Lyne combined smartly down the right before the latter delivered a pass for Kershaw to slide in at the corner in the 26th minute.
It perhaps gave his side too much confidence, though, as soon after Joe Westerman wasted another good attacking position with an ill-conceived flick pass that went to ground and allowed Saints loose forward Morgan Knowles to race upfield.
The supporting Percival was eventually hauled down by fellow England centre Lyne but James Batchelor was deemed to have hung around in the ruck too long and he was duly yellow-carded.
Saints immediately tried to make the extra man count but, when frustrated, instead accepted another Coote penalty when Trinity strayed offside.
However, the 12-man hosts dug deep and scored a second try just before the interval.
Miller spotted space down the left and his lofted pass saw 21-year-old Senior surge in, avoiding Coote’s desperate challenge.
Lino converted from the touchline with the last kick of the half but - despite those valiant efforts - his side could not force a shock defeat.
Wakefield Trinity: Hampshire; Kershaw, Lyne, Arundel, Senior; Miller, Lino; Arona, Batchelor, Tanginoa, Pitts, Ashurst, Westerman. Substitutes: Fifita, Battye, Aydin, Kay.
St Helens: Coote; Grace, Naiqama, Percival, Makinson; Dodd, Lomax; Walmsley, Roby, Amor, Mata’utia, Batchelor, Knowles. Substitutes: Lees, Thompson, Paasi, Welsby.
Referee: Ben Thaler (Wakefield)