Northampton Saints had two players sent off as they finished the Heineken Champions Cup group stage with defeat by defending champions La Rochelle.

Lock Lukhan Salakaia-Loto received a red card in the final moments.

La Rochelle ran in five tries to ensure a home tie in the last 16, while Saints finish bottom of Pool B with one point.

Lawes, who limped off in the 29th minute, has struggled with injuries this season and must now see if he will be fit for the start of the Six Nations, which begins on 4 February.

Saints took an early lead through Fin Smith's penalty kick but the French side, seeking to maintain their 100% group record, scored the first try when Levani Botia forced his way over.

Dingwall was sent off for a high tackle on Dillyn Leyds, who had to be replaced after failing a head injury assessment.

Saints only trailed 7-3 at half-time but the French side dominated the second half, with two tries from replacement hooker Quentin Lespiaucq-Brettes and one apiece for Ulupano Seuteni and Gregory Alldritt.

The visitors' scrum-half Tawera Kerr-Barlow was sin-binned for a deliberate offside and replacement Tom James capitalised to score Saints' only try.

To complete Saints' miserable day, Salakaia-Loto was sent off in the last minute for leading with his forearm.

'Red card turned everything'

Northampton head coach Phil Dowson said: "Just before half-time, I thought we were in a good space but the red card turned everything.

"I can't fault the effort but our performance wasn't good enough in certain areas. Our discipline was poor and I have no complaints about the two dismissals."

Asked about Lawes' injury, Dowson added: "Courtney doesn't appear to be downbeat - he never is - but he felt he couldn't continue.

"His calf tightened up. He hasn't had an issue with it before but he will need to see the physio tomorrow and possibly have a scan, so it's fingers crossed."

Line-ups

Northampton: Furbank, Freeman, Dingwall, Hutchinson, Skosan, F Smith, Braley; E Waller, R Smith, Painter, Salakaia-Loto, Ribbans, Lawes, Hinkley, Ludlam (c).

Replacements: Haywood, Hobbs-Awoyemi, Petch, Coles, Scott-Young, James, Sleightholme, Ramm.

Red cards: Dingwall (39), Salakaia-Loto (80)

La Rochelle: Dulin, Leyds, Seuteni, Favre, Rhule, Hastoy, Kerr-Barlow; Wardi, Lagrange, Atonio, Sazy, Picquette, Botia, Bourdeau, Alldritt (c).

Replacements: Lespiaucq, Sclavi, Colombe, Lavault, Dillane, Boudehent, Berjon, Thomas.

Match officials

Referee: Andrea Piardi (Italy)

Touch judges: Eoghan Cross, Dan Carson (both Ireland)

TMO: Joy Neville (Ireland)