[7] With Robert Lui leaving the club at the end of 2011, Sironen was considered a possible replacement for the Wests Tigers halfback, along with players Jacob Miller, Tim Moltzen and Tom Humble.

[6] Moltzen started the season at halfback, but a number of players filled the position before Benji Marshall moved from five-eighth.

According to reports, Sironen's ex-partner hacked into his Twitter account and posted a naked photo of him with another woman with the caption "I make excuses this is why my girlfriend who is tattooed on my arm left me".

After Taylor was terminated, Paul Sironen said "He punted me then got rid of my young bloke last year, Well, karma's a bitch, Good riddance & don't let the door hit you on the way out!".

[21] In the 2018 NRL season, Sironen only managed to feature in 4 games for Manly as he missed the majority of the year with a knee injury which required a reconstruction.

Sironen missed out on playing in the club's final series due a foot injury sustained in Manly's round 25 loss against Parramatta.

[28] It was announced in September 2021 that Sironen had signed a two-year deal with the reigning English Super League champions St Helens RLFC for the 2022 season.

[citation needed] In round 1 of the 2022 Super League season, Sironen made his club debut for St Helens R.F.C.

[31] In round 3 of the 2023 Super League season, Sironen was sent to the sin bin during St Helens 25-24 controversial loss against Leeds.

[32] Sironen played 15 games for St Helens in the 2023 Super League season as the club finished third on the table.

Sironen played in St Helens narrow loss against the Catalans Dragons in the semi-final which stopped them reaching a fifth successive grand final.

[33] Sironen played 21 matches for St Helens in the 2024 Super League season which saw the club finish sixth on the table.