PEORIA, Ariz. – The Mariners’ pitching rotation figures to be one of the club’s top strengths.

Fronted by long-time ace Felix Hernandez, the unit posted the American League’s third-best ERA even though Hisashi Iwakuma and Taijuan Walker opened the season on the disabled list and James Paxton missed four months because of a strained back muscle.

Veteran right-hander Chris Young, the A.L.’s comeback player-of-the-year, departed through free agency, but the Mariners replaced him by acquiring lefty J.A. Happ from Toronto in a trade for outfielder Michael Saunders.

The rotation is deep and balanced and offers a nice blend of proven veterans and high-ceiling youngsters who have already logged major league time.

It’s a nice mix.

The locks

Manager Lloyd McClendon says he views the rotation as having just one opening.

He also says Happ will be in the unit.

That sets up a front four of Hernandez, Paxton, Iwakuma and Happ.

The guess here is Paxton draws the No. 2 slot over Iwakuma in order to provide the Mariners with a right-left-right-left balance.

If Paxton stays healthy, and the others pitch to career norms, it should be a formidable unit.

Spring battles

The projected competition between Walker and Roenis Elias for the final spot figures to be the camp’s biggest story line.

Elias pitched well last season as a rookie making the jump from Double-A Jackson and would, on many other clubs, slot as a lock into the middle of the rotation.

But Walker has long been viewed as the Seattle organization’s top pitching prospect and flashed signs last September of realizing that potential.

A point to note: Erasmo Ramirez is still just 24, but he’s out of options.

It’s hard to see him cracking the rotation, barring multiple injuries, but he’s also unlikely to clear waivers. He could be a candidate for a long relief job.

Help if needed

Since either Walker or Elias will likely open at Triple-A Tacoma, the rotation can absorb one major injury.

(Yes, Hernandez would be particularly hard to replace.)

Club officials are anxious to get a look at lefty Danny Hultzen, who appears healthy after missing most of the last two years because of major shoulder problems.

Hultzen will, almost certainly, be on an innings-limit this season, but if he approaches his pre-injury form – he was the No. 2 overall pick in the 2011 draft, remember – he could provide a down-the-stretch boost.

No.	Player	B-T	Primary 2014 club	W-L	ERA
29	Roenis Elias	L-L	Mariners	10-12	3.85
33	J.A. Happ	L-L	Toronto	11-11	4.22
34	Felix Hernandez	R-R	Mariners	15-6	2.14
60	Danny Hultzen	L-L	Injured	N/A	N/A
18	Hisashi Iwakuma	R-R	Mariners	15-9	3.52
59	Mike Kickham	L-L	AAA Fresno	8-8	4.43
65	James Paxton	L-L	Mariners	6-4	3.04
50	Erasmo Ramirez	R-R	Mariners	1-6	5.26
32	Taijuan Walker	R-R	AAA Tacoma	6-4	4.81
Non-roster invites (6)
No.	Player	B-T	Primary 2014 club	W-L	ERA
58	Sam Gaviglio	R-R	AA Springfield	5-12
49	Justin Germano	R-R	AAA Round Rock	4-13	4.51
61	Stephen Landazuri	R-R	AA Jackson	6-5	4.33
66	Tyler Olson	L-L	AA Jackson	10-7	3.52
74	Jordan Pries	R-R	AAA Tacoma	9-8	4.06
64	Forrest Snow	R-R	AAA Tacoma	2-3	4.05