Morgan Whittaker scored the only goal against former club Swansea to give Plymouth their first away victory of the season.
The striker – who left the Swans in a £1million move in July last year – scored in the 18th minute to give the Pilgrims a 1-0 win.
It was Whittaker’s 17th goal of a profitable season and his ninth in his last 10 games as Argyle made it six games without defeat.
Back-to-back Championship defeats and a fourth loss in a row in all competitions leaves Swansea head coach Luke Williams still searching for his first league win since he took charge.
It also leaves the Swans just five points clear of the relegation zone.
Liam Cullen struck the bar late on, but Swansea lacked accuracy in front of goal and missed several good chances.
Both clubs had been active on transfer deadline day and their respected line- ups reflected their work.
Swansea duo Przemyslaw Placheta and Charles Sagoe Jr were among their substitutes, while Ronald – who joined the club earlier in the week – was given his first start.
For Plymouth, Lino Sousa – like Sagoe Jr, an Arsenal loanee – was named on the bench.
After Swansea’s Ben Cabango had spurned an early chance by lashing a shot high and wide from the edge of the six-yard box, Whittaker gave early indications of his threat.
The deep-lying striker’s opening gambit was thwarted when Nathan Wood blocked a shot, before Whittaker tested Carl Rushworth with a stinging volley the Swansea keeper just about managed to tip over.
From the corner, Plymouth fashioned a goal. Adam Forshaw started the move and then found Whittaker with a pass which the striker clipped nonchalantly, first-time, low into the corner from the edge of the box.
Swansea had already felt an injustice when a penalty appeal for a push on Ollie Cooper was turned down, but their failure to level before half-time lay with themselves.
New signing Ronald – a £1.5m buy from Brazilian club Gremio Anapolis – twice set up his team-mates from the right wing, but neither chance was taken.
Firstly, Jamie Paterson skied his shot over the bar. Then, Jerry Yates allowed Plymouth keeper Conor Hazard to save after the Swans striker met another accurate Ronald cross into the goalmouth.
It was the same story at the start of the second half as Yates mis-directed his header wide of the near post from the Brazilian’s delivery.
If Argyle were riding their luck a little, they were also still looking dangerous enough to improve their lead on the counter-attack.
Just before the hour mark, Mickel Miller fired over the bar after two team-mates had shots blocked in a frantic few seconds.
Swans’ substitute Placheta looked lively after coming on for his debut, but when the Polish winger created space for himself on the edge of the box, his effort was well clear of the bar.
Placheta then crossed for fellow substitute Cullen, but the striker was unable to beat Hazard from close range.
Swansea were now building a head of steam as Plymouth tired and came nearest to an equaliser when Cullen’s dipping shot struck the top of the crossbar in the 84th minute.
Hazard also saved from substitute Charlie Patino in the third minute of added time.
Southampton 3-1 West Brom (3-1 agg): Saints set up play-off final with Leeds United
Southampton saw off West Brom 3-1 at St Mary's on Friday to set up a Championship play-off final showdown with Leeds United.
Leeds thumped Norwich City 4-0 at Elland Road 24 hours earlier to book their place at Wembley, where Southampton now await on May 26.
The first leg between the Saints and West Brom finished goalless - just like the other semi-final - but the home side's quality told in the end.
Russell Martin's side dominated the first-half possession, with David Brooks going closest to scoring with a shot that hit the outside of the post.
Southampton made the breakthrough via a powerful Will Smallbone finish four minutes into the second half after Gray Diangana lost possession.
Darnell Furlong had a shot helped over by Alex McCarthy, while David Brooks - who assisted the opener - had a strong penalty appeal rejected.
Southampton remained in control, though, and Adam Armstrong scored a second with a shot through Furlong's legs and past Alex Palmer.
Armstrong's second goal arrived from the penalty spot in the 86th minute after Tom Fellows fouled Ryan Manning in the box, rendering Cedric Kipre's late header a mere consolation.
Al-Nassr 1-1 Al-Hilal: Mitrovic scores last-gasp penalty
Aleksandar Mitrovic scored a penalty in the 10th minute of second-half stoppage time as Al-Hilal denied Cristiano Ronaldo's Al-Nassr victory in a 1-1 draw.
Mitrovic netted his 27th Saudi Pro League goal of the campaign after Sadio Mane was harshly judged to have fouled Saud Abdulhamid in the area.
Mane stuck out an arm to shield the ball, catching his opponent in the throat, though the contact appeared to have been outside of the box.
Mitrovic made no mistake to keep Al-Hilal's unbeaten campaign going.
The Serbian's spot-kick cancelled out Otavio's first-minute opener, with Ronaldo having set up his compatriot.
Champions Al-Hilal remain 12 points clear of Al-Nassr at the summit of the Pro League standings.
Data Debrief: Ronaldo the provider
Ronaldo leads the scoring charts in Saudi Arabia this season, though he had to settle for an assist on Friday.
That came from the only chance he created, with the 39-year-old limited to 25 touches, though he did have four shots.
Leeds' belief never wavered as Wembley beckons
Ethan Ampadu said Leeds United's players never let their belief waver despite a poor end to their Championship campaign, with a trip to Wembley now coming up.
Leeds will face either Southampton or West Brom in the play-off final on May 26 after thrashing Norwich City 4-0 at Elland Road on Thursday.
The Whites endured a miserable end to their campaign, losing 4-0 at Queens Park Rangers before going down at home to Southampton on the final day, as Ipswich Town claimed automatic promotion behind Leicester City.
But after their emphatic defeat of the Canaries, who they drew with 0-0 in the first leg, Ampadu claimed Leeds never lost their way.
"Towards the end of the season there was a lot of talk about how we were playing, how we weren't on the front foot, how we weren't aggressive or clinical," he told Sky Sports.
"But we always had our belief that on our day, when we are firing, we can be hard for anyone to play against.
"When the front four, five, six play like that, they make the job of us defenders a lot easier.
"Whoever we play in the final it's going to be a hard game but to go in like this, to put in a performance like this, we can take momentum and confidence into it.
"The fans were second to none and we enjoyed their support – now we are going to prepare for the big one."
Georginio Rutter scored one and set up another in the rout, and he put the onus on Leeds to replicate the same level at Wembley.
"It's incredible. Today we go to Wembley," he said.
"We played a good game. I'm happy, everybody is happy. One more game and we will see.
"We played very good. 4-0 is a clean sheet. Today, we were mature. It's a very good performance from the team.
"I want to try my best and help the team. If we play like this [at the final], we have a good chance but we have to play like this."
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