The arena Pro Swim Series hits Mesa, Arizona this weekend. Many swimmers are coming off short-course seasons — high school, college — and transitioning over to long course, and the summertime season.

And now that we’re firmly cemented into 2017, most swimmers look ahead. This summer could provide an opportunity for the next generation of swimmers to step-up. With the departure of several Olympians, international roster spots are opening, momentum is shifting, and we’re entering a new Olympiad.

As always, here are your 5 Storylines…

1. NCAA swimmers finding their long-course groove.

The transition from short-course to long-course is not an easy one. Especially after spending an entire season at the NCAA level, where the difference between a loss and victory may be a short-course turn. While many swimmers have spent the last several months perfecting all the nuances of short-course, now, in Mesa, it’s long-course once again. And there’s perhaps no better event to kick-off the weekend than the women’s 100m freestyle, featuring American record-holder Simone Manuel, Katie Ledecky, Amanda Weir, and more.

2. On the men’s side, veterans return to the competition pool.

Nathan Adrian and Anthony Ervin are like the Energizer bunnies: They keep going. 35-year-old Ervin looks like he’ll never slow down. Adrian looks to defend his status as our nation’s best sprinter. If last month’s NCAA Championships served as a platform to advertise the nation’s next generation of sprinters, this weekend serves as a reminder that many veteran sprinters are still competing at top-form.

3. Leah Smith emerging as her own force.

Is there any swimmer more overshadowed, as far as mainstream media is concerned, than Leah Smith? In many other non-Ledecky eras, Smith would be dominant. Her 400m time is incredible. Watch for Smith to continue to improve, and inch towards Tokyo 2020. Though it’s hard not to watch Ledecky blast through the water and break world record after world record, Smith continues to swim consistently well.

4. Tom Shields seeks butterfly dominance.

If anyone gains from Phelps’ retirement (as far as a purely competitive advantage is concerned), it’s 25-year-old Tom Shields. Of course, anytime you have the Greatest competing, it raises the bar. So Phelps’ retirement may be a disadvantage, too. But at the same time, butterflyers like Shields are finally thrust into the spotlight. Look for Shields to attempt a double victory this weekend, though he’ll have his hands full, especially in the 100m distance.

5. Katie Ledecky

At this point, no words are needed. Whenever Ledecky competes, she’s her own storyline. What we’re seeing is unprecedented in the recent history of the sport. Complete dominance. A thrashing of the record books. How long can Ledecky continue to drop time? How low can she go? We’ll see.