ESPN's rugby predictions: Games of the week, potential upsets & more

It is another huge week across the Aviva Premiership, PRO14 and Top 14 as table toppers face huge battles to keep their title challenges intact. Who are the players to watch, the games of the weekend and potential upsets across the leagues?

With Exeter Chiefs and Leicester Tigers facing off against each other, the PRO14 derbies continuing and the latest the ongoing struggles of Toulon, here is ESPN's preview of the weekend's action.

Player to watch

Prem (Martyn Thomas): Tatafu Polota-Nau (Leicester). Following two appearances as a replacement, the Wallaby hooker will make his first start for the Tigers when they travel to champions Exeter Sunday. It promises to be a baptism of fire for Polota-Nau as he goes up against England hopeful Luke Cowan-Dickie. Leicester boss Matt O'Connor will hope his new hooker can deliver as the Tigers attempt to halt a run of five consecutive defeats.

PRO14 (Cillian O Conchuir): Thomas Farrell (Connacht). The centre has lit up the PRO14 this season, beating the most defenders and having the most offloads in the competition to date. Four tries so far this season and making a name for himself alongside Bundee Aki at centre in the west of Ireland, if Connacht can climb up the rankings, and injuries strike Joe Schmidt's team, an Ireland call up could be around the corner.

Top 14 (James Harrington): Ben Botica (Oyonnax). After a short and difficult stint at Montpellier, the former Harlequin joined Oyonnax as a medical joker early in 2017 - and has quickly become a crowd favourite at Stade Charles Mathon. There have admittedly been few high points for the club this season, but Botica has been the architect of most of the good things that they have done. Last season's Pro D2 champions need him at his best if they are to beat Racing 92 and start clawing their way back into a relegation dogfight that, frankly, they look to have already lost.

Game of the weekend

Prem: Exeter vs. Leicester, Sunday, 3 p.m.

Hosts Exeter have opened up a 10-point lead at the top of the Premiership as they welcome Leicester to Sandy Park. Their European stutter was forgotten with a commanding performance and Rob Baxter's side will be confident of victory against an out of sorts Tigers. But Leicester have far too much quality to continue on their current run, and if the likes of George Ford, Jonny May, Matt Toomua and Manu Tuilagi fire then they could give the champions a fright.

PRO14: Ulster vs. Munster, Monday, 5:35 p.m.

In what is a huge game for both teams, Ulster will want to resurrect their playoff hopes which have faltered of late. They sit seven points behind Leinster and defeat, at home, against Munster would make it a bigger challenge. Munster, 12 points behind Glasgow in their own conference, could be pulled back into a playoff dogfight with defeat, with third-placed Cheetahs having two games in hand after this weekend's games.

Top 14: Toulouse vs Toulon, Saturday, 7.45 p.m.

Toulon ended a four-match losing run against Toulouse back in September, when young fly-half Anthony Belleau guided them to a 20-16 victory at Stade Mayol. Now, in the first weekend of the second-half of the Top 14 season, Toulouse will be looking for revenge -- and the chance to overtake their opponents in the standings.

Potential Upset

Prem: Bath vs. Wasps, Friday, 7.45 p.m.

Bath's seesaw season continued last weekend as they followed up an impressive win over Toulon with a narrow defeat at Newcastle. Wasps arrive at the Recreation Ground in fine form, having won six of their last seven matches and despite a run of injuries displayed their strength in depth last time out to secure a bonus-point win over in-form Gloucester, Kyle Eastmond was one player who impressed against the Cherry and Whites and will be keen for a positive result on his return to Bath.

PRO14: Leinster vs. Connacht, Monday, 3.15 p.m.

Connacht will take plenty of inspiration from their mauling of Ulster last weekend, and if Leinster are looking ahead to crucial European Cup games, this provides the possibility of an upset for Connacht. Victory for Kieran Keane's men could also push them towards an automatic Champions Cup spot for next season which is their main goal this season.

Top 14: Clermont vs Castres, Sunday, 3 p.m.

Clermont's Stade Marcel Michelin is a graveyard for visiting teams. And, under normal circumstances, this match would be chalked off as another routine victory for the hosts. But these are a not normal circumstances. Reigning champions Clermont are struggling with an injury list longer than their 'Association Sportive Montferrandaise Clermont Auvergne' name. Visitors Castres, meanwhile, are riding a six-match Top 14 winning streak dating back to early October. Three years ago, they ended Clermont's 76-match, five-year hot streak at home. Repeating that trick is a very real possibility.

Big Weekend for

Prem: Northampton. It was confirmed Friday morning that Alan Gaffney would arrive at Franklin's Gardens as an interim consultant on New Year's Day and in the last match before he takes the reins, Saints players must stake a claim for their jersey. Over the past month or so Northampton have been too easily beaten as standards have slipped, and while relegation is unrealistic they are long overdue a win. Twickenham, against Harlequins, would be a fitting stage on which to get it.

PRO14: Glasgow and Edinburgh. Expect a backlash from Dave Rennie's side after losing their 100 percent record last week. If Edinburgh are not well prepared it could get very ugly, but despite their struggles, they could move into the Champions Cup automatic spot if they record back-to-back wins over Glasgow, and Ulster fail to get anything from their clash with Munster. Defeat for Glasgow could also sew doubt into their players' minds after 10 wins in a row.

Top 14: Jacques Brunel. On Wednesday, FFR president Bernard Laporte formally announced what everyone had suspected for some time -- that Bordeaux boss Brunel was the man to replace Guy Noves as head coach of France. But, he has one last Top 14 job to do before settling in to the hotseat at Marcoussis -- prepare his team for Saturday afternoon's trip to struggling Stade Francais.