Glasgow Warriors and Edinburgh face a run of fixtures over the coming weeks which will define their seasons.
Warriors, the defending Pro12 champions, have found momentum hard to come by this term, currently sitting eighth in the league.
They also face an uphill battle to make the Champions Cup quarter-finals.
Edinburgh are faring rather better, occupying third place in the Pro12 and still in the hunt for the knockout stages of the European Challenge Cup.
Scotland's record cap holder and points-scorer Chris Paterson examines how both Scottish clubs have performed this season and looks ahead to what the rest of the season holds for both Glasgow and Edinburgh.
Glasgow's struggle for momentum
After several seasons of steady and sustained progress, Glasgow made the breakthrough last year by clinching the Pro12 title in unforgettable style against Munster.
Following that triumph with more of the same was always going to be a tough ask, especially with Warriors being forced to make do without the 20 players who represented their countries at the Rugby World Cup.
Gregor Townsend's men could still go on a run to put them right in the mix come the business end of the season, but they have displayed their undoubted class only sporadically so far in this campaign.
Back-to-back 1872 Cup losses to Edinburgh and defeat away to Racing 92 in the Champions Cup means Warriors are on a three-game losing streak, and are in danger of seeing their two main targets - defending the Pro12 title and progressing to the knockout stages in Europe - slip away.
Paterson, though, thinks the quality within Glasgow's squad means they could yet find find their best form to go on a winning streak, starting with their make-or-break European clash with Northampton on Sunday.
"It's a crucial part of the season," Paterson told BBC Scotland.
"The two games against Edinburgh were both very similar. Edinburgh deserved to win both, their defence was outstanding. Two good, high quality games. As a Scotsman it was good to see that combative style of both teams.
|Glasgow's next three games:|
|Sun 17 Jan: Northampton (A) - European Champions Cup|
|Sat 23 Jan: Racing 92 (H) - European Champions Cup|
|Fri 29 Jan: Ospreys (A) - Pro 12|
"After those three defeats for Glasgow they are rewarded with a trip to Franklins Gardens and Northampton who beat them pretty soundly at Scotstoun. I know that hurt a lot of the guys at Glasgow, the players and the staff.
"But they have put a lot right since that happened, especially up front, in the scrum. Northampton's domestic form hasn't been great but they are a quality team.
"It's a big, big ask for Glasgow but it's this time of year that the pressure comes on and you have to deliver. They've got a quality coaching staff, a quality group of players. We've seen that, we've seen them win silverware and they'll need all their experience in the next two or three weeks."
Edinburgh starting to click
After being cast as a mere sideshow in the shadows of Glasgow's success in recent years, Edinburgh now find themselves in a good place.
They are just four points behind Pro12 leaders Scarlets in the league table, and victory over Agen on Friday night at Murrayfield will keep them in contention to reach the knockout stage of the Challenge Cup, a competition they reached the final of last season.
"I think quite rightly they have to target the top end of the table," Paterson said.
"With a defence like that they are hard to beat. They're in the top four at the moment, and similarly to Glasgow it's a crucial period of the season. They'll want to go into the Six Nations still in that top four.
"They'll want to finish off the two games in Europe with victories. Keeping that momentum going that Edinburgh have found will be really important and it should set them up for a big season finale."
Edinburgh's style of play has been a source of great debate, with many believing the tactics employed by coach Alan Solomons do not encourage expansive, attacking rugby.
"They're doing what suits them, they're winning," says Paterson, who played for Edinburgh between 1999 and 2007 and again from 2008 to 2012.
"It's not great to watch at times but it's effective. Purists look at style but the professional game is ultimately about results.
|Edinburgh's next three games:|
|Fri 15 Jan: Agen (H) - European Challenge Cup|
|Sat 23 Jan: Grenoble (A) - European Challenge Cup|
|Sat 30 Jan: Cardiff Blues (A) - Pro 12|
"Edinburgh have a fantastic defence, a great set piece and that's their strengths. They are continually adding to their attack. Duncan Hodge is in there and you can see the influence he is trying to bring with the shape and they are trying to play, but it takes a lot of work.
"Edinburgh did so well in the European Challenge Cup last year, they're in a good position this year as well. This weekend's game against Agen is crucial. If they can win at home then it sets up a big final fixture against Grenoble."