Twelve teams kicked off with dreams of Premiership success and silverware in September. Now, in late May, just four remain as we reach the semi-finals.

Defending champions Saracens and last season's runners-up Exeter Chiefs appear favourites to book a repeat of their 2018 final after finishing in the top two.

But Gloucester and Northampton Saints stand in their way and will hope to spring a surprise (or two).

BBC Sport looks ahead to both matches on Saturday with the help of BBC Radio 5 Live's Rugby Union Weekly podcast pundits Ugo Monye and Danny Care.

Saracens v Gloucester (Allianz Park, 13:30 BST)

Second against third from the regular season go head-to-head first up on Saturday as Saracens host Gloucester in what will be the 3,000th game of Premiership rugby since the competition began in 1987.

Saracens have lost just once in their past five semi-final appearances while Gloucester find themselves paired against Sarries for the third time in the last four.

How do the pundits see this one unfolding?

Ugo Monye, former Harlequins, England and British and Irish Lions winger:

"Gloucester beat Saracens at Kingsholm earlier in the season, but they were well beaten at Saracens. They had 50-odd points put on them.

"But Gloucester stand a much better chance than Northampton of causing an upset this Saturday as they and Saracens are the two fresher sides going into the semi-finals.

"You just wonder what lessons Gloucester have learned from that heavy defeat. But they've got to take care of their own game and they've got to take it to an extraordinary level to beat Saracens.

"If we look at what this Saracens team have done, especially in the European Champions Cup final, you've got to be better than anything you've ever put together this season - set-piece, defence, attack, kick-chase, work-rate.

"That's where you've got to be to beat the best team in Europe. Gloucester have got one key operating cog in their system in Premiership player of the season Danny Cipriani.

"He's assisted more tries than anyone, but it'll take more than just try assists.

"You've got to have the full package to beat the best team in Europe.

"For Cipriani to have a blinder, it means his pack have got to play well. If he doesn't have a blinder, it's because the guys in front of him haven't played well.

"But you can't rely on Cipriani throwing 50-yard passes and pulling rabbits out of hats for 80 minutes to beat Saracens."

Danny Care, Harlequins and England scrum-half:

"Gloucester need their best performance of the year and I think they also need Saracens to have an off-day.

"From watching Saracens first-hand in that Champions Cup final, if they defend anything like they did that day, they'll be impossible to shift.

"Cipriani cannot do what he does without his pack giving him the ball, without centres Mark Atkinson and Billy Twelvetrees on his outside running those lines for him."

Exeter v Northampton (Sandy Park, 16:30 BST)

Once the first semi-final is over, attention shifts to Devon where first-placed Exeter and fourth-placed Northampton will have a definite feeling of deja vu.

These two met each other just last Saturday at the same venue in the last game of the regular season with Chiefs eventually powering through to win 40-21.

But will that dress rehearsal tell us anything about what to expect now that it's a winner-takes-all affair?

Exeter are in their fourth Premiership semi-final in as many years, all of which have been at home, while Northampton are in the last four for the first time since 2015.

Ugo Monye: "How are Northampton going to be able to overturn that 19-point deficit from last weekend?

"Exeter weren't at their very best, but what I was impressed with was how Northampton really went at it in the first 20 minutes. But they couldn't sustain it for 80 minutes.

"That's their task this weekend. If they can, then they've got a chance.

"I don't think Exeter's scrum is anywhere near where it could be. If Northampton are to get a foothold in the game, then it's the scrum.

"Exeter do give up scrum penalties, but it's what you do with the ball when you do have it.

"If Exeter get 60% possession, they'll tear you apart like they did last Saturday. If you can keep hold of it, then you've got every chance."

Danny Care: "Exeter needed to win last weekend to finish first.

"It must've been tough mentally those last few games, where you know you've got a home semi-final, getting up for games when you don't want to get injured, you just want to get through and get to the meaningful games.

"It was massively important for them that they got back to winning ways and they've put a massive marker down against the team they're facing in the semi-final.

"They'll be full of confidence now and I think they'll be in the final. But it's a one-off game - you've got every chance and anything can happen.

"If Northampton can keep hold of the ball for long enough, they've got some unbelievable players. Taqele Naiyaravoro on the wing is a freak, it takes two or three people to tackle him.

"If they can keep hold of the ball for longer and be more clinical with it, they'll be in with a shout.

"When Exeter get the ball, they keep it for minutes and minutes and minutes - and just grind you down and score tries."

And who makes it to Twickenham?

Ugo Monye: "Statistically, 83% of play-off semi-finals have been won by the home side.

"I think they'll be two great games and the stats would dictate that the home sides will be favourites, but throw stats out of the window for an emotional, one-off game.

"You've got to give everyone a chance.

"It's been a crazy year and I'm not saying it's going to be a Gloucester-Northampton final, but if you're in the top four, I just don't think at this point it's fair to write those teams off."

Danny Care: "I'd be very surprised if it wasn't a Saracens-Exeter final.

"I'd be surprised if Northampton can overturn that 19-point deficit in a week, so Exeter will be in the final.

"I can't see Gloucester going to Saracens and winning, so it will be a Saracens-Exeter final."